System and method for performing in-service optical fiber network certification

ABSTRACT

A system and method for performing an in-service optical time domain reflectometry test, an in-service insertion loss test, and an in-service optical frequency domain reflectometry test using a same wavelength as the network communications for point-to-point or point-to-multipoint optical fiber networks while maintaining continuity of network communications are disclosed.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is filed under 37 C.F.R. §1.53(b) as acontinuation-in-part claiming the benefit under 35 U.S.C §120 of thepending U.S. patent application Ser. No. 12/233,495, “System and Methodfor Performing In-Service Fiber Optic Network Certification”, which wasfiled by the same inventors on Sep. 18, 2008 claiming the benefit under37 C.F.R. §1.53(b) of U.S. patent application Ser. No. 10/793,546 filedon Mar. 3, 2004 by the same inventors and now issued as U.S. Pat. No.7,428,382 on Sep. 23, 2008, which claims the benefit under 35 U.S.C.119(e) of U.S. Provisional Application No. 60/451,614, filed Mar. 3,2003, now expired, and entirely incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates generally to optical fiber communication networks,and more specifically to the network certification, diagnostic testing,and optical measurement of an optical fiber network.

BACKGROUND OF THE INVENTION

Troubleshooting, maintenance, and related administration to supportcustomer's service level agreements (SLA) are a large part of an OpticalFiber Network Operator's operational expenses (OpEx) for optical fibernetworks. The labor and material costs for troubleshooting anddiagnosing maintenance or service outage problems within an opticalfiber network can dominate an Operator's operating budgets and impactcustomer's SLAs negatively. Operators have deployed redundant networksthat have multiple optical fiber links with automatic loss of linkdetection and switchover capabilities to insure SLAs and other missioncritical services are maintained.

Usually when optical fibers are first deployed, highly skilled personnelor technicians with expensive fiber test equipment are assigned the taskof ensuring and verifying desired optical fiber plant link budgets aremet. This process of fiber plant deployment occurs before service isenabled to customers or during out-of-service periods, which are closelymonitored and sometimes restricted due to customer's SLA constraints.All Long Haul, Metro and Access optical fiber networks are similarlydeployed in this manner.

Once a customer or subscriber service is enabled, Operators areresponsible for the troubleshooting, maintenance and servicing requiredby the optical fiber links as they degrade over time. This places extracost burden on the fiber plants to provide field testability. Typicallythis field testability requires extra splitters at ends of optical fiberlinks to allow the connection of optical test equipment. Each additionalsplitter not only means more capital expense (CapEx) is incurred by theOperator but it also takes away precious dBs from the optical linkbudget. Operators greatly value their fiber plant optical link budgetswhere reach and other optical link margin related policies are used todifferentiate its service offerings at an optical fiber link level.Operators thus use non-network affecting optical test methods likeOptical Time Domain Reflectometry (OTDR) using specialized hand-helddevices which use maintenance wavelengths, or optical supervisionchannels, such as 1625 nm wavelength that is separate and independentfrom all other wavelengths used to carry customer service network datacommunications. This is a capital and labor intensive method for routinefiber maintenance checks while ensuring service outages do not occur.

Therefore performing optical fiber network certification or atroubleshooting procedure or maintenance procedure without therequirement for manual troubleshooting, additional maintenancesplitters, and without the requirement for a separate and dedicatedmaintenance wavelength is highly desirable to Operators due to realizedOpEx, CapEx and optical link budget savings.

BRIEF SUMMARY OF THE INVENTION

The embodiments of the present invention provide for multiplexing anin-service optical time domain reflectometry (ISOTDR), an in-serviceoptical frequency domain reflectometry (ISOFDR), or an in-serviceinsertion loss (ISIL) test session or a combination thereof using thesame wavelength as the data communication signals for point-to-point orpoint-to-multipoint optical fiber networks while in synchrony withphysical layer and data link layer protocols used for establishing,maintaining, administering and terminating network data communications.

Referring now to FIG. A, a flowchart summarizing the process ofin-service testing and certification of optical fiber networks inexemplary embodiments of the present invention is shown. Aspects ofembodiments of the invention can include one or more of the followingfeatures. Initiating a test method A00, such as an in-service OTDR(ISOTDR), in-service Insertion Loss (ISIL), or in-service OFDR (ISOFDR)test or a combination thereof can be done by an application layer entitysuch as a Network Certification Service Entity (NCSE) (embedded orexternal to an optical network terminal or apparatus). The NCSE amongother duties provides a Multiplexing Service Entity (MSE) with testmethod parameters. The MSE interfaces with a network protocol in-usehaving predetermined time intervals or frames for data communications toschedule, allocate or grant times for frames or messages required tocoordinate and multiplex test method events in synchrony with thenetwork protocol A02. When the scheduled, allocated or granted time orwindow to perform the test method has arrived A04 the MSE then causes aPhysical Layer Service Entity (PLSE) to transmit a test signal insynchrony with the network protocol A06 otherwise the MSE waits A08 forthe allocated time or window A04. If the test method involves an ISOTDRor an ISOFDR test method A10 then light transmissions cease for apredetermined time after the test signal transmission to facilitatedmeasurements of the optical reflections and backscatter from thetransmitted test signal. Measurements of the reflections and backscatterare performed at the same optical network terminal performing the testsignal transmission A12. If the test method is an ISIL test method A10then light transmissions need not cease and the test signal can continueto be transmitted for the duration of the test method. IL measurementsof the test signal are performed at a desired or intended receivingoptical network terminal(s) A14. Durations for ISIL only test methodscan be much shorter in time duration than test methods involving OTDR orOFDR due to the IL only test method does not require time to measureoptical reflections or backscatter. In some embodiments, analysis ofmeasurements at the optical network terminal A16 performing ameasurement of a test method can be performed and alarms either visual(e.g., LED indication) or network protocol based can be issued A18. Inembodiments with external servers (e.g., at a Network Operations Center(NOC) or data center or cloud compute farms) the measurements can betransmitted through network control or data channels to the externalservers for analysis which can then raise alarms or issue networkcertification reports A20. In some embodiments, measurements can betransmitted through network control or data channels to other opticalnetwork terminals which can then analyze and issue alarms orcertification reports A20.

In one aspect of an embodiment of the invention the optical fibernetwork is a point-to-multipoint optical fiber network such as ITU-TG.984 Gigabit PON (G-PON), ITU-T G.987 10 Gigabit PON (XG-PON), IEEE802.3ah Ethernet PON (EPON), IEEE 802.3av 10 Gigabit Ethernet PON(10G-EPON), WDM-PON, ITU-T G.983 (BPON), and RFoG SCTE IPS910, SCTE 1742010.

In one aspect of an embodiment of the invention the optical fibernetwork is a point-to-point optical fiber network such as ActiveEthernet IEEE 802.3ah, Gigabit Ethernet IEEE 802.3z, 10-Gigabit EthernetIEEE 802.3ae, 40-Gigabit Ethernet and 100-Gigabit Ethernet IEEE 802.ba,SONET/SDH as defined by GR-253-CORE from Telcordia and T1.105 fromAmerican National Standards Institute, Ethernet over SONET/SDH (EoS),Metro Ethernet Forum (MEF) Metro Ethernet, MPLS based Metro Ethernet,IEEE 802.3 Ethernet and Fibre Channel.

In one aspect of an embodiment of the invention a sequence or patternfor bit clock recovery is transmitted after the predetermined time withno light transmissions.

In one aspect of an embodiment of the invention the test methodmeasurements are analyzed to determine transmitter couplingefficiencies.

In one aspect of an embodiment of the invention the test methodmeasurements are analyzed to detect and locate optical fiber linktampering.

In one aspect of an embodiment of the invention the test methodmeasurements are analyzed to determine microbends or macrobends in oneor more optical fiber link.

In one aspect of an embodiment of the invention the test methodmeasurements are analyzed to determine insertion loss between to opticalnetwork terminals.

In one aspect of an embodiment of the invention the test methodmeasurements are analyzed to determine optical return loss of atransmitting optical network terminal.

In one aspect of an embodiment of the invention the test methodmeasurements are analyzed to determine reflectance of distal opticalnetwork terminals.

In one aspect of an embodiment of the invention the test methodmeasurements are analyzed to determine mean launch power of atransmitting optical network terminal.

In one aspect of an embodiment of the invention the test methodmeasurements are analyzed to determine the location and characteristicsof impairments such as optical fiber splices, optical fiber connections,optical splitters, and optical fiber segment loss in one or more opticalfiber links.

In one aspect of an embodiment of the invention the test signal includesone or more light transmissions, each comprised of a desired pattern ofintensity, frequency, wavelength and duration.

In one aspect of an embodiment of the invention an ISOTDR, ISIL, orISOFDR test method or some combination thereof are performed whencommunications between optical network terminals are beingunderutilized, or in lieu of idle packets or silence periods and upon adisruption in communications between optical network terminals.

In one aspect of an embodiment of the invention the optical signals sentover an optical fiber can be continuous mode or burst modecommunications.

In one aspect of an embodiment of the invention wavelength divisionmultiplexing (WDM), course wavelength division multiplexing (CWDM), ordense wavelength division multiplexing (DWDM) can be used and a testmethod performed on any wavelength.

In one aspect of an embodiment of the invention a type field in a frameused for communications is used to indicate a specific test method orinform of a specific test method being performed.

In one aspect of an embodiment of the invention direct digital synthesisto generate a frequency sweep for OFDR test methods can be used.

In one aspect of an embodiment of the invention the payload lengthindicator (PTI) within GPON encapsulation method (GEM) header is used toindicate an extension of the GEM frame used for test methods.

In one aspect of an embodiment of the invention a unique network trafficaddress or identifier is used to indicate or be associated with a testmethod.

In one aspect of an embodiment of the invention an ALLOC-ID isassociated with a test method to provide for upstream bandwidthallocation for a test method to be performed.

In one aspect of an embodiment of the invention a Port-ID is used toindicate or be associated with a test method.

In one aspect of an embodiment of the invention an LLID is used toindicate or be associated with a test method.

In one aspect of an embodiment of the invention an operationadministration management (OAM) message is used to configure test methodparameters of a test method associated with a unique network addressidentifier at an optical network terminal.

In one aspect of an embodiment of the invention a Physical Layer OAM(PLOAM) message is used to configure the test method associated with anAlloc-ID or Port-ID.

In one aspect of an embodiment of the invention an OAM message is usedto configure the test method associated with an LLID.

In one aspect of an embodiment of the invention a PLOAM message is usedto configure the test method associated with an LLID.

In one aspect of an embodiment of the invention a plurality of bits inthe flag field of an upstream bandwidth map in GPON is used to indicatethe reference frame for the stop time of an allocation.

In one aspect of an embodiment of the invention OAM messages are used toconvey test method results.

In one aspect of an embodiment of the invention PLOAM messages are usedto convey test method results.

In one aspect of an embodiment of the invention OMCI messages are usedto convey test method results.

In one aspect of an embodiment of the invention GEM is used toencapsulate and convey test method results.

In one aspect of an embodiment of the invention Ethernet data frames areused to convey test method results.

In one aspect of an embodiment of the invention Ethernet MAC controlframes are used to indicate a test method is being performed and conveytest method parameters to the PCS layer.

In one aspect of an embodiment of the invention flow control mechanismsand Ethernet MAC control frames are used to create or schedule a PAUSEtime period during which a test method is performed.

In one aspect of an embodiment of the invention control code groups areused to inform the PMA layer of a test method being performed.

In one aspect of an embodiment of the invention control code groups areused to indicate timing of segments of a test method being performed tothe PMA layer.

In one aspect of an embodiment of the invention the PMA layer cancontrol the PMD layer and control the timing of test methods and receiveresults of test methods.

In one aspect of an embodiment of the invention the PCS layer cancontrol the PMD layer and control the timing of test methods and receiveresults of test methods.

In one aspect of an embodiment of the invention Multipoint MAC ControlProtocol (MPCP) control frames are used to indicate a test method isbeing performed and convey test method parameter to the PCS layer.

In one aspect of an embodiment of the invention MPCP control frames areused to create or schedule a PAUSE time period during which a testmethod is performed.

In one aspect of an embodiment of the invention MPCP sub-layer entityissues Grants to send an OAM message for requesting an Ethernet PAUSE.

In one aspect of an embodiment of the invention MPCP sub-layer entityissues Grants to perform a test method.

In one aspect of an embodiment of the invention a signal used toestablish bias voltage across an avalanche photo-diode (APD) isinversely proportional to a signal used to disable the opticaltransmitter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. A illustrates a state block diagram in accordance with anembodiment of the present invention;

FIG. 1A illustrates optical network terminals and an optical fiber datanetwork in accordance with an embodiment of the present invention;

FIG. 1B illustrates a point-to-multipoint system in accordance with anembodiment of the present invention;

FIG. 2A is a block diagram which illustrates the OSI 7-layer model;

FIG. 2B is a block diagram which illustrates various entities of anoptical network system in accordance with an embodiment of the presentinvention;

FIG. 3 is a block diagram which illustrates the block level circuitryand components of a portion of an optical network terminal of a opticalfiber data network in accordance with an embodiment of the presentinvention;

FIG. 4A is a block diagram which illustrates an OSI reference model andrelated entities of a point-to-multipoint ITU-T GPON or XG-PON Head-endOLT system in accordance with an embodiment of the present invention;

FIG. 4B is a block diagram which illustrates an OSI reference model andrelated entities of a point-to-multipoint ITU-T GPON or XG-PON ClientONU/T system in accordance with an embodiment of the present invention;

FIG. 5 is a block diagram which illustrates the block level circuitryand physical and data link layers of an OLT and ONU/T of an ITU-T GPONor XG-PON optical fiber data network in accordance with an embodiment ofthe present invention;

FIG. 6A is a block diagram which illustrates a diagrammatic flow of thedownstream communications in an ITU-T G.984 GPON and ITU-T G.987 XG-PONnetworks incorporating test methods in accordance with an embodiment ofthe present invention;

FIG. 6B is an illustration of a table describing the meaning of PTIwithin the GEM header and incorporating test methods in accordance withan embodiment of the present invention;

FIG. 6C is a flow chart summarizing a method of incorporating testmethods in downstream communications of ITU-T G.984 GPON and ITU-T G.987XG-PON networks in accordance with an embodiment of the presentinvention;

FIG. 6D is an illustration of the PLOAM message format and examples forassigning ALLOC-ID and configuring a test method associated with aPort-ID in accordance with an embodiment of the present invention;

FIG. 6E is an illustration of a table describing the meaning of bitvalues in the Flag field of the Upstream Bandwidth Map (US BW Map) fieldin accordance with an embodiment of the present invention;

FIG. 7A is a block diagram which illustrates a diagrammatic flow theupstream communications in a ITU-T G.984 GPON and ITU-T G.987 XG-PONnetworks incorporating test methods in accordance with an embodiment ofthe present invention;

FIG. 7B is an illustration of a table describing the meaning of bitvalues in upstream PLOAM field in accordance with an embodiment of thepresent invention;

FIG. 7C is a flow chart summarizing a method of incorporating testmethods in upstream communications of ITU-T G.984 GPON and ITU-T G.987XG-PON networks in an embodiment of the present invention;

FIG. 8 is a block diagram which illustrates the block level circuitry orcomponents of a portion of an optical network terminal of an opticalfiber data network in accordance with an embodiment of the presentinvention.

FIG. 9A is a block diagram which illustrates an OSI reference model andrelated entities of a point-to-point IEEE GE or 10GE active EthernetHead-end OLT system in accordance with an embodiment of the presentinvention;

FIG. 9B is a block diagram which illustrates an OSI reference model andrelated entities of a point-to-point IEEE GE or 10GE active EthernetClient ONU/T system in accordance with an embodiment of the presentinvention;

FIG. 10 is a block diagram which illustrates a diagrammatic flow of thecommunications in a point-to-point IEEE GE or 10GE active Ethernetsystem incorporating test methods in accordance with an embodiment ofthe present invention;

FIG. 11A is an illustration of a table describing the meaning of controlcode groups and a test method control code group for Ethernetcommunications in accordance with an embodiment of the presentinvention;

FIG. 11B is a block diagram which illustrates a diagrammatic flow oftest methods in the Physical layer in accordance with an Ethernetembodiment of the present invention;

FIG. 11C is a block diagram which illustrates the block level circuitryand physical and data link layers of an OLT and ONU/T of apoint-to-point IEEE GE or 10GE active Ethernet optical fiber datanetwork in accordance with an embodiment of the present invention;

FIG. 11D is a flow chart summarizing a method of incorporating testmethods in communications of IEEE 802.3 point-to-point (P2P) Ethernetnetworks in accordance with an embodiment of the present invention;

FIG. 12A is a block diagram which illustrates an OSI reference model andrelated entities of a point-to-multipoint IEEE 10G-EPON EthernetHead-end OLT system in accordance with an embodiment of the presentinvention;

FIG. 12B is a block diagram which illustrates an OSI reference model andrelated entities of a point-to-multipoint IEEE 10G-EPON Ethernet ClientONU/T system in accordance with an embodiment of the present invention;

FIG. 13A is a block diagram which illustrates a diagrammatic flow of thedownstream communications in a point-to-multipoint IEEE 10G-EPONEthernet system incorporating test methods in accordance with anembodiment of the present invention;

FIG. 13B is a block diagram which illustrates a diagrammatic flow of theupstream communications in a point-to-multipoint IEEE 10G-EPON Ethernetsystem incorporating test methods in accordance with an embodiment ofthe present invention;

FIG. 14A is a block diagram which illustrates a diagrammatic flow ofdownstream test methods in the Physical layer in accordance with anEthernet embodiment of the present invention;

FIG. 14B is a block diagram which illustrates a diagrammatic flow ofupstream test methods in the Physical layer in accordance with anEthernet embodiment of the present invention;

FIG. 14C is a block diagram which illustrates the block level circuitryand physical and data link layers of an OLT and ONU/T of apoint-to-multipoint IEEE 10GE-PON Ethernet optical fiber data network inaccordance with an embodiment of the present invention;

FIG. 14D is a flow chart summarizing a method of incorporating testmethods in upstream communications of IEEE 802.3av 10G-EPON networks inan embodiment of the invention

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to various embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction withthese embodiments, it will be understood that they are not intended tolimit the invention to these embodiments. On the contrary, the inventionis intended to cover alternatives, modifications and equivalents, whichmay be included within the spirit and scope of the invention as definedby the appended claims. Furthermore, in the following description of thepresent invention, numerous specific details are set forth in order toprovide a thorough understanding of the present invention. In otherinstances, well-known methods, procedures, components, and circuits havenot been described in detail as not to unnecessarily obscure aspects ofthe present invention.

The method and system of the present invention can coexist with existingnetwork protocols or be engineered into future network protocols todetermine the condition or characteristics of optical fiber links,including optical network terminals and optical components whichcomprise an optical fiber network. Conventional approaches used todetermine the condition of optical fiber links include OpticalTime-Domain Reflectometry (OTDR), Optical Loss test (also known asInsertion Loss Test and used as such throughout this disclosure) andOptical Frequency Domain Reflectometry (OFDR). The TelecommunicationsIndustry Association (TIA) has developed many standards covering theOTDR and Insertion Loss test approaches and these standards (e.g.,TIA/EIA-526-7, TIA/EIA-526-14, TIA/EIA TSB-140, TIA/EIA-568.B, etc) areincluded herein by reference.

The OTDR approach or test method involves transmitting a light pulse ora series of light pulses of a desired wavelength, such as a wavelengthused for data communications, into one end of an optical fiber undertest and then measuring from the same end of the optical fiber theportion of light that is reflected back due to Rayleigh scattering andFresnel reflection. The intensity of the reflected light is measured andintegrated as a function of time and plotted as a function of opticalfiber length. OTDR is used for estimating the optical fiber, splitter,and connection losses as well as locating faults, such as breaks in anoptical fiber.

In addition to a single optical fiber, OTDR can also be used withmultiple optical fibers. For example, when several optical fibers areconnected to form an installed fiber plant or optical distributionnetwork (ODN) (e.g., a passive optical network comprised of opticalfiber links interconnected with optical splitters, optical combiners,optical filters, and possibly other passive optical components), OTDRcan be used to characterize optical fiber and optical connectionproperties along the entire length of the optical fiber links of thefiber plant. A fiber plant is comprised of optical fiber links which arecomprised of optical fiber path or waveguide, connectors, splices,mounting panels, jumper cables, and other passive components.

As described above, in addition to OTDR, Insertion Loss is anothermethod used to determine the condition of optical fiber links. TheInsertion Loss method involves transmitting a light pulse or acontinuous light signal of known optical power or strength and of adesired wavelength into a first end of the optical fiber under test andthen measuring the received optical power or amount of light received ata second end of the optical fiber. The difference between thetransmitted optical power and the received optical power is calledinsertion loss or optical loss. The insertion loss can indicate a faultor failure to meet optical link margin in an optical fiber link if thevalue is great, indicating the received optical power is too low toensure accurate signal transmission. Additionally, knowledge of theinsertion loss between any combination of transmitters and receivers onan optical fiber link enables the light output power setting on thetransmitter to be set at a minimum or optimum setting to ensure accuratesignal transmission while saving power and extending the life of thetransmitter(s).

OFDR is a method of detecting optical reflections and backscattering inthe frequency domain. OFDR uses an optical carrier (e.g., acommunication signal wavelength) modulated by a periodic linearfrequency sweep as a test signal for transmission on an optical fiber.An inverse Fourier transform of the received response can produce adistance-domain map of the optical fiber and used to assescharacteristics of the optical fiber. OFDR is especially useful tomeasure reflecting elements or components that generate Fresnelreflections such as optical connectors.

Traditionally, OTDR, OFDR, and Insertion Loss Testing are performed whenthe optical fiber network is “out of service.” For example, duringinitial fiber plant installation and deployment, network technicians useopto-electronic test instruments to perform OTDR, OFDR or Insertion Losstesting after each splice or fiber connection is made. The term “out ofservice” means the continuity of data communications is interrupted orbroken (e.g., interruption of a video stream or a VoIP call). As notedin the Background of the Invention as set forth above, conventional “outof service” maintenance and servicing of optical fiber networksincreases overall network costs and decreases network efficiency.

Unlike conventional methods and devices, the present invention usescontrol of optical transmitters and receivers in synchrony with thenetwork protocol having predetermined time intervals or frames for datacommunications of an optical fiber network to test and characterizeoptical fiber links and optical connection properties along the entirelength of the optical fiber link(s) while the optical fiber network is“in-service.” The term “in-service” means the continuity of datacommunications is maintained or preserved (e.g., no interruption of avideo stream or a VoIP call). Since the invention uses the networkprotocol having predetermined time intervals or frames for datacommunications and a plurality of optical transmitters and receivers ofa given optical fiber network while the network is operational orin-service to perform an OTDR test, OFDR test or an Insertion Loss test,the systems and methods of the present invention are respectivelyreferred to herein as In-Service Optical Time-Domain Reflectometry(ISOTDR), In-Service Optical Frequency Domain Reflectometry (ISOFDR),and In-Service Insertion Loss (ISIL). As will be shown, in addition tousing either an ISOTDR test method, ISOFDR test method or ISIL testmethod to determine the condition or characteristics of optical fiberlinks, the ISOTDR, ISOFDR and ISIL test methods can also be combined orperformed simultaneously. This combination is referred to herein asISOTDR-ISIL, ISOFDR-ISIL, and ISOTDR-ISOFDR-ISIL. Generally speaking anyand all ISOTDR, ISOFDR, ISIL, ISOTDR-ISIL, ISOFDR-ISIL andISOTDR-ISOFDR-ISIL test methods are simply referred to throughout thespecification as the test methods.

As previously mentioned, the present invention can coexist with existingnetwork protocols having predetermined time intervals or frames for datacommunications or be designed into future network protocols havingpredetermined time intervals or frames for data communications, whichcan be conceptualized using the Open Systems Interconnection (OSI)reference model. The OSI reference model was established by theInternational Standards Organization (ISO) and is hereby included byreference (ISO/IEC 7498-1). The following description is provided tobetter understand the flow of data signals through the OSI model.

Referring now to FIG. 2A, wherein like reference numerals designateidentical or corresponding parts throughout several views, figures andembodiments and wherein cascading boxes below a part designates aplurality of such parts, the OSI 7-layer model 200 is an abstract modelof a networking system divided into layers, numbered 1 through 7. Withineach layer, one or more entities implement the functions of a layer.Additionally, each layer provides services to the other layers adjacentto it, thereby forming a modular framework and allowing diverse entitiesat potentially any layer to communicate with each other. As definedherein, entities are active protocol elements in each layer that aretypically implemented by means of software or hardware processes atpoints, nodes, computers or terminals on the optical network. Entitiesin the same layer on different computers or optical network terminalsare called peer entities. In general, optical network terminals arenetwork apparatus that send and receive signals on an end of an opticalfiber link. At each layer of the OSI model 200, there can be more thanone entity that can implement different protocols depending on thelayer.

In embodiments of the invention, shown in FIG. 2B, a networking systemincludes the following entities: a network certification service entity(NCSE) 250,255, a multiplexing service entity (MSE) 251,254 and aphysical layer service entity (PLSE) 252,253, wherein each of theseentities can be implemented in hardware, software or a combinationthereof and comprise a plurality of sub-entities. Although the functionsassociated with each entity and the interactions between entities aredescribed herein with reference to specific communication networkprotocols further discussed below in reference to FIGS. 4A-7C and FIGS.9A-14D, it is understood that a variety of communication networkprotocols can not only be used but are envisioned.

In general, PLSE 252,253 coordinates and performs the functions requiredby the test methods and resides at the physical layer of the OSI model.The MSE 251,254 is served by the PLSE 252,253 and causes the functionsof scheduling, allocating, granting times for frames or messagesrequired to coordinate and multiplex test method events in synchronywith the data communication protocol of the optical fiber network. TheMSE 251,254 can reside at the same OSI layer as the PLSE 252,253 or canreside at an OSI layer above the PLSE 252,253 (e.g. data link layer).The NCSE 250,255 is served by the MSE 251,254 and the NCSE isresponsible for initiating test methods, establishing values orparameters required by the MSE and PLSE to perform test methods,receiving the results or measurements of the test methods, analyzingreceived test method results or measurements, and can issue opticalfiber network certification reports. The NCSE 250,255 can reside at thesame OSI layer as the MSE 251,254 or at an OSI layer above the MSE251,254 (e.g., application layer).

A Network Management System (NMS) is a combination of hardware andsoftware used to monitor and administer a network. Individual networkelements (NEs) in a network (e.g., optical network terminals) aremanaged by an Element Management System (EMS). In an embodiment of theinvention, at least one NCSE 250,255 can be implemented as softwarerunning on a server that interfaces with, or is part of, an NMS. Inanother embodiment, at least one NCSE can be implemented as acombination of hardware and software running on a server that interfacewith, or is part of an EMS. In yet another embodiment, at least one NCSEcan be implemented as a combination of hardware and software residingwithin one or more capable optical network terminals of the opticalfiber network. Exemplary embodiments of capable optical networkterminals are optical line terminal (OLT) 150 and optical network unit(ONU) 155, and optical network terminal (ONT) 160 of FIG. 1B discussedfurther below.

An ONT is a single integrated electronics unit that terminates anoptical fiber network and presents native service interfaces to an enduser or subscriber. An ONU is an electronics unit that terminates theoptical fiber network and may present one or more converged interfaces,such as xDSL or Ethernet, toward the end use or subscriber. An ONUtypically requires a separate subscriber unit to provide native userservices such as telephony, Ethernet data, or video. In the hybrid fibercoaxial network case, ONUs/ONTs are called nodes, optical nodes or eventaps depending on where the fiber network ends and the coaxial cablenetwork begins. In practice, the difference between an ONT and ONU isfrequently ignored, and either term is used generically to refer to bothclasses of equipment and in this specification ONU/ONT and ONU/T termsare used to refer to either an ONU or ONT.

As disclosed above, the NCSE 250,255 is, in general, responsible forinitiating test method requests and establishing values or parametersneeded by the MSE and PLSE to perform test methods. The NCSE 250,255 canestablish MSE parameter values such as test type, network terminaladdresses to perform the test, test burst window period, delay period,measurement sampling period and bit clock recovery pattern or sequence.The NCSE 250, 255 can also establishes PLSE parameter values such asoptical intensity (i.e., optical power), frequency or pattern of one ormore transmissions of light and their durations the sampling resolutionof test light transmission measurements for the test methods. Thesevalues are referred hereto as test method parameters.

To identify, and thereby characterize, the target optical fiber link108, the NCSE 250,255 discovers all capable optical network terminaladdresses, relative to the network protocol used by the MSE and PLSE,which are capable of performing the test methods. The NCSE 250,255 usesthe services of the network protocols 200 to determine the capableoptical network terminal addresses. For example, in an embodiment of theinvention, before receiving a request to perform test methods at a givennetwork layer address (e.g., IP address) of a capable optical networkterminal, an NCSE 250,255 application entity can use the dynamic hostconfiguration protocol (DHCP) application layer protocol for IPv4networks to retrieve an assigned IP address and other configurationinformation in lieu of manually configuring NCSE IP address by ServiceProvider or Network Operator technicians. Similarly, extensions for DHCPfor IPv6 (DHCPv6) can be used by NCSE 250,255 application entity toretrieve an assigned IP address. Now that NCSE 250,255 has a networklayer address (IP address) the address resolution protocol (ARP) forIPv4 networks can be used, given the received network layer address, todetermine the MSE 251,254 data link layer address or media accesscontrol (MAC) address of the capable optical network terminal. Similarlythe neighbor discovery protocol (NDP) can be used by NCSE 250,255 todetermine the MSE 251,254 data link layer address or MAC address of thecapable optical network terminal on IPv6 networks. If the NCSE 250, 255is unable to determine which capable optical network terminals share thesame optical fiber link, then the NCSE 250, 255 requests a peer orservice entity (e.g., as part of the NMS or EMS) to disclose whichcapable optical network terminals share the same optical fiber linkwithin the optical fiber network. After the capable optical networkterminals are identified, the NCSE 250, 255 is then able to map allcapable optical network terminal addresses 256, 257 to every capableend-point on the optical fiber network.

In an alternative embodiment, the NCSE 250,255 can use the services ofthe network protocols 200 to determine which capable optical networkterminals share the same optical fiber link. As previously disclosed,this allows the NCSE 250,255 to map all capable optical network terminaladdresses to every capable end-point on the optical fiber network. Forexample, in an embodiment of the invention, the NCSE 250 can use DHCP,as previously discussed, to retrieve its network IP address and request,via the simple network management protocol (SNMP), a peer OLTAdministration entity 404 (FIG. 4A) for the MSE 251 data link layeraddress in lieu of using the previously mentioned ARP method todetermine the capable optical network terminal address that share acommon optical fiber link. This embodiment relies on the OLTAdministration entity 404 to provide the necessary network layer addressto data link layer address translation functions required for the NCSE250 to establish communications with MSE 251 which intern providescommunications with PLSE 252. Once the NCSE 250,255 knows which capableoptical network terminals share the same optical fiber link, the NCSE250,255 then identifies the specific capable optical network terminaladdress that will be involved in the desired optical fiber link test andinitiates the desired test methods.

In yet another alternative embodiment, to initiate the test methods, theNCSE 250,255 can send the IP addresses of the identified capable opticalnetwork terminals and method test parameters to the MSE 251,254 via thenetwork protocol services without peer OLT Administration entityproviding the necessary network layer address to data link layer addresstranslation functions. This can be done by MSE 251,254 using bootstrapprotocol (BOOTP) or DHCP to obtain its network IP address from aconfiguration server managed by the Service Provider or NetworkOperator. The NCSE 250,255 network IP address is determined by usingDHCP as previously mentioned. After initiating the test methods, theNCSE 250,255 receives test results or measurements data of the testmethods from the MSE 251,254. This embodiment relies on the MSE 251, 254obtaining a network IP address independently from the NCSE 250,255obtaining the MSE network IP address. The NCSE can discover an MSEnetwork IP address by sending a query request to a domain name system(DNS) server. Alternatively, the MSE can discover the NCSE network IPaddress by sending a network IP address query request to a DNS server;and once the NCSE network IP address is obtained then the MSE registersitself with the NCSE so that the NCSE knows the MSE network IP addressbefore initiating the desired test method. It will be appreciated thatNCSE and MSE can use Object Request Broker (ORB), such as Common ObjectRequest Broker Architecture (CORBA), for communications andinteractions. While NCSE and MSE are discussed above in terms of networklayer and data link layer addresses and related service entities, ORBscan utilize the same or similar addresses and service entities toperform communications in alternative embodiments.

To analyze and interpret the results of the test methods, the NCSE 250,255 can initiate a plurality of test methods while varying test methodparameters to obtain results or measurements for some or allpermutations of capable optical network terminal connections within theoptical fiber network. In addition, the NCSE 250,255 can use the resultsor measurements obtained from peer NCEs 255,250 that have previouslyperformed the test methods on the optical fiber network.

In addition to the above-referenced functions and services, the NCSE250,255 can provide network certification report services to peerentities or service entities that reside at any OSI layer, such as thoseshown in FIG. 2A. These network certification report services caninclude descriptions of the state or condition of individual opticalfiber links or characteristics of specific optical fiber link elements(e.g., connectors, splices, etc.) within a given optical fiber networkduring in-service periods or partial in-service periods. A partialin-service period is defined as the period wherein a specific opticalfiber link has failed causing out-of-service periods for that part ofthe optical fiber network. The NCSE network certification reportservices cover a variety of network components and characteristicsincluding, but not limited to, conditions of individual optical fiberlinks, such as the location and loss profile of fiber splices, fiberconnectors, optical splitters, fiber macrobends, fiber microbends,insertion loss, reflectance of optical network terminals, optical fibersegment loss, mean launch power of transmitting optical networkterminal, transmitter optical coupling efficiency, and optical fiberlink tampering. The network certification report services can includeOTDR trace data and can conform to Telcordia GR-196 standard format.

In an alternative embodiment of the invention, the NCSE 250, 255 canalso determine the effective transceiver optical coupling efficiency ofan optical network terminal. The resulting network certification reportcan thereby be used to aid the process of reconciling and mitigatingdiscrepancies of fault isolation and differences between test methodresults and non-test method results obtained with separate and dedicatedoptical fiber test equipment (e.g., hand held test equipment).

In general, it will be appreciated that the NCSE network certificationreport services can cause peer and service entities to initiateoperational, administrative and maintenance events, such as alarms,flags, plots, human resource assignments, service layer agreement (SLA)updates or optical component procurement orders, that are used byService Providers and Network Operators to manage a given optical fibernetwork in a financially optimal manner. In addition, the NCSE servicesprovide Service Providers and Network Operators with the ability tominimize the overall capital and operational expenses of an opticalfiber network during in-service periods, during periods when serviceoutages are being repaired, and during periods when services are beingreestablished.

The NCSE services can, in an embodiment of the invention, also provideService Providers and Network Operators with the ability to monitor anentire optical fiber network to ensure physical fiber or physical layersecurity can be maintained at all times. For example, if a malicioususer or individual attaches an apparatus to an optical fiber linkdesigned to intercept the optical signals in an effort to unlawfullydiscover information, then the NCSE services are used to detect thefiber tampering, generate a security alert, and identify the location ofthe malicious tampering event, all of which can be performed while theoptical fiber network continues to be in-service.

In an embodiment of the invention, the NCSE 250, 255 can detect a fibertampering event has occurred by periodically comparing new test methodresults with previously stored test method results, assuming the storedmethod results cover the entire optical fiber network and the opticalfiber links tested by the new method results eventually cycle over theentire optical fiber network. If the results of NCSE comparisons showany discrepancies or differences between the previously stored methodresults, then a tampering event can be declared and the NCSE 250,255 canprovide the approximate location of the tampering, based on the analysisof the latest test method results, to requesting entities who can thensuspend network services to affected optical network terminals.

As previously disclosed in an embodiment of the invention the MSE251,254 causes the functions of scheduling, allocating, granting timesfor frames or messages required for coordinating events that are neededto perform the various test methods. In general, the MSE 251,254receives an initiated test method request from a NCSE 250,255. If thereceived test method request is not addressed to the PLSE 252, 253 onthe same optical network terminal as the MSE 251,254, then the testmethod request can be forwarded to the appropriate peer MSE 254,251 withthe addressed PLSE via the network protocol or in alternativeembodiments the request can be ignored. In this regard, the MSE 251,254can use the network protocol to translate addresses. However, if thereceived request pertains to the MSE 251,254 then the MSE 251,254schedules, in synchrony with the network protocol having predeterminedtime intervals or frames for data communications, the optimal time givennetwork congestion or idleness to perform the requested test method onthe optical fiber network. The MSE 251,254 determines the optimal timevia services of the network protocol at or below the layer of the MSE251,254 and from deductions made by the MSE 251,254 from the test methodparameters of the received requested test method. An example, in anembodiment of the invention, of a MSE deduction includes, but is notlimited to, the amount of time necessary to accomplish the requestedtest method taking into account the line rate or communication rate ofthe optical fiber link(s) involved.

If the requested test method is an ISIL, ISOTDR-ISIL, ISOFDR-ISIL orISOTDR-ISOFDR-ISIL test method, then the MSE 251,254 also schedules atime, via or in synchrony with the network protocol, to receive theresults of the insertion loss measurements. In addition, any peer MSE(s)254,251 that is also involved with the requested test method is alsoinformed, via and in synchrony with the network protocol, of thescheduled time that the requested test method will be performed.Further, the MSE 251,254 can also send to the PLSE 252,253, on the sameoptical network terminal as the MSE 251,254, the test method parametersand the capable optical network terminal addresses received from thetest method request in time for the now scheduled test method to beperformed by the PLSE 252,253 via and in synchrony with the networkprotocol.

As disclosed above and referring to FIG. 2B, in general a PLSEcoordinates the functions required to perform the test methods andexists at the physical layer of the OSI model. The PLSE 252,253 receivesfrom the MSE 251,254 a request to perform a test method together withthe associated test method parameters and capable optical networkterminal addresses involved in performing the requested test method. Ingeneral, the PLSE 252,253 performs the requested test method bytransmitting necessary test signals or test light transmissions,disabling light transmission and, in some instances depending on thetest method (e.g., OTDR, OFDR), measuring the reflected test signal ortest light transmissions. Further, the PLSE 252,253 can measure the testsignal or test light transmissions from another PLSE that shares theoptical fiber link, again depending on the test method (e.g. ISIL).

In addition to the OSI model, the present invention will now bedescribed with respect to a high-level overall representation of anoptical fiber network. Referring to FIG. 1A, embodiments of high-leveloverall representation of optical network terminals of an optical fibernetwork in accordance with the present invention includes a firsttransceiver 100 in communication with a second transceiver 101 via anoptical fiber 108. As shown in FIG. 1A, the first transceiver 100 andthe second transceiver 101 include optical transmitter circuitry (Tx)134, 135 to convert electrical data input signals into modulated lightsignals for transmission over optical fiber 108. In addition, the firsttransceiver 100 and the second transceiver 101 also include opticalreceiver circuitry (Rx) 133, 136 to convert optical signals received viaoptical fiber 108 into electrical signals and to detect and recoverencoded data and clock signals. Furthermore, first transceiver 100 andsecond transceiver 101 can contain a micro controller, cpu, or othercommunication logic and memory 131, 132 necessary for network protocoloperation. Although the illustrated and described embodiments of thetransceivers 100, 101 include a micro controller, embedded cpu, or othercommunication logic and memory in the same package or device as theoptical transmitter circuitry 134, 135 and optical receiver circuitry133, 136, other embodiments of transceivers can also be used (e.g., asdiscrete or separate components or some combination thereof).

As shown in FIG. 1A, the first transceiver 100 transmits and receivesdata signals to or from the second transceiver 101 in the form ofmodulated optical light data communication signals of known wavelengthvia optical fiber 108. The transmission mode of the data signals sentover the optical fiber 108 can be continuous, burst or both burst andcontinuous modes depending on the implementation of an embodiment.Alternatively, in another embodiment both transceivers 100,101 cantransmit or receive a same wavelength (e.g., the light signals arepolarized and the polarization of light transmitted from one of thetransceivers is perpendicular to the polarization of the lighttransmitted by the other transceiver). In another embodiment a singlecommunication signal wavelength can be used by both transceivers 100,101 (e.g., the transmissions are in accordance with a time-divisionmultiplexing scheme or similar communication protocol).

In yet another embodiment in accordance with the invention,wavelength-division multiplexing (WDM) can also be used. WDM is hereindefined as any technique by which two optical communication signalshaving different wavelengths can be simultaneously transmittedbi-directionally with one wavelength used in each direction over asingle optical fiber. In one embodiment, coarse wavelength-divisionmultiplexing (CWDM) or dense wavelength-division multiplexing (DWDM) canbe used. CWDM and DWMD are herein defined as any technique by which twoor more optical data communication signals having different wavelengthsare simultaneously transmitted. The difference between CWDM and DWDM isCWDM wavelengths are typically spaced 20 nanometers (nm) apart, comparedto 0.4 nm spacing for DWDM wavelengths. Both CWDM and DWDM can be usedin bi-directional communications. In bi-directional communications,(e.g., if wavelength division multiplexing (WDM) is used), the firsttransceiver 100 can transmit data signals to the second transceiver 101utilizing a first communication signal wavelength of modulated lightconveyed via optical fiber 108 and, similarly, the second transceiver101 can transmit data signals via the same optical fiber 108 to thefirst transceiver 100 utilizing a second communication signal wavelengthof modulated light conveyed via the same optical fiber 108. Because onlya single optical fiber is used, this type of transmission system iscommonly referred to as a bi-directional transmission system. Althoughthe optical fiber network illustrated in FIG. 1A includes a firsttransceiver 100 in communication with a second transceiver 101 via asingle optical fiber 108, other embodiments of optical fiber networks,such as those having a first transceiver in communication with aplurality of transceivers via a plurality of optical fibers (e.g., shownin FIG. 1B), can also be used as well as those having a first and secondtransceiver in communication over a plurality of optical fiber (e.g.109,110).

As shown in FIG. 1A, electrical data input signals (Data IN 1) 115, aswell as any optional clock signal (Data Clock IN 1) 116, are routed tothe transceiver 100 from an external data source (not shown) forprocessing by the communication logic and memory 131. Communicationlogic and memory 131,132 processes the data and clock signals inaccordance and in synchrony with a network protocol in-use betweentransceivers. Communication logic and memory 131,132 provide managementfunctions for received and transmitted data signals including queuemanagement (e.g., independent link control) for each respective link,demultiplexing or multiplexing and other functions described furtherbelow. The processed signals produced are transmitted by the opticaltransmitter circuitry 134. The resulting modulated light signalsproduced from the first transceiver's 100 optical transmitter 134 arethen conveyed to the second transceiver 101 via optical fiber 108. Thesecond transceiver 101, in turn, receives the modulated light signalsvia optical receiver circuitry 136, converts the light signals toelectrical signals, processes the electrical signals via thecommunication logic and memory 132 in accordance and in synchrony withan in-use network protocol and can output or forward the result throughelectrical data output signals (Data Out 1) 119, as well as any optionalclock signals (Data Clock Out 1) 120.

Similarly, the second transceiver 101 receives electrical data inputsignals (Data IN 1) 123, as well as any optional clock signals (DataClock IN) 124, from an external data source (not shown) for processingby the communication logic and memory 132 and transmission by opticaltransmitter circuitry 135. The resulting modulated light signalsproduced from the second transceiver's 101 optical transmitter 135 arethen conveyed to the first transceiver 100 via optical fiber 108. Thefirst transceiver 100, in turn, receives the modulated light signals viaoptical receiver circuitry 133, converts the light signals to electricalsignals, processes the electrical signals via the communication logicand memory 131 in accordance with an in-use network protocol and canoutput the result through electrical data output signals (Data Out 1)127, as well as any optional clock signals (Data Clock Out 1) 128.

It will be appreciated that first 100 and second 200 transceivers of theoptical fiber data network 140 of the present invention can also includea plurality of electrical input and clock input signals, denoted hereinas Data IN N 117/125 and Data Clock IN N 118/126, respectively, and aplurality of electrical output and clock output signals, denoted hereinas Data Out N 129/121 and Data Clock Out N 130/122, respectively. Theinformation provided by the plurality of electrical input signals can beused by a given transceiver to transmit information via optical fiber108 and, likewise, the information received via optical fiber 108 by agiven transceiver can be outputted by the plurality of electrical outputsignals. The plurality of electrical signals denoted above can becombined to form data plane or control plane bus(es) for input andoutput signals respectively. In some embodiments of the invention, theplurality of electrical data input signals and electrical data outputsignals are used by logic devices or other devices located outside (notshown) a given transceiver to communicate with the transceivercommunication logic and memory 131,132, transmit circuitry 134,135, andreceive circuitry 133,136.

Since the PLSE as previously discussed, is located at the physical layerin the OSI model and the responsibilities of the PLSE involve opticaltransmit and receive functions, embodiments of the PLSE include controlof transmit and receive circuitry. Referring to the exemplary embodimentof a portion of an optical network terminal of FIG. 3 and in view ofFIG. 1A, the communication logic and memory 131,132, the transmitcircuitry 134,135 and the receive circuitry 133,136 of the transceivers100,101 are further illustrated and now discussed. When desired, thecommunication logic and memory 131,132 transmits outgoing data signalsvia electrical signals 323 to the laser Driver (Driver) 322 which can bea continuous mode or burst mode laser driver. The Driver 322 drives anoptical transmitter such as Laser Diode (LD) 315, which transmits lightdata signals in response to modulation current or bias current ofelectrical signals 323. The modulation current typically corresponds tohigh data values, such as logic 1, and a bias current typicallycorresponds to low data values, such as logic 0. As such, the LD 315transmits light in response to the modulation and bias current.

The light emitted from LD 315 travels into optical fiber 108 with theaid of the fiber optic interface 301. The fiber optic interface 301optically couples the LD 315 and an optical receiver such asPhotoDetector or PhotoDiode (PD) 311 to optical fiber 108. The fiberoptic interface 301 can include, but is not limited to, optical filters,beam splitters, and lenses. The fiber optic interface 301, as depictedin this embodiment of the invention, includes lenses 303,302 to aid inthe visualization of the optical coupling provided by interface 301.

Referring now to the transceiver 100,101 of FIG. 3 and in view of FIG.1A, the transceiver 100,101 receives data signals in the form of lighttransmissions along optical fiber 108 that travel through the fiberoptic interface 301 and are received by PD 311. In response, PD 311provides a photocurrent to the TransImpedance Amplifier (TIA) 312 thatconverts the photocurrent into an electrical voltage signal. Theelectrical voltage signal from TIA 312 is then sent to the DigitalSignal Recovery (DSR) circuitry 314 (which includes clock and datarecovery (CDR)), which converts the electrical voltage signals intodigital signals. The DSR circuitry 314 can further detect digitalwaveforms within the electrical voltage signal and output a well-defineddigital waveform. Finally, the digital waveform is sent as received datasignal input to the communication logic and memory 131,132.

In general, light transmissions of the transceiver 100,101 arecontrolled by controller such as the communication logic and memory131,132. As shown in FIG. 3, the communication logic and memory 131,132communicates with the transceiver controller (trcv controller) 325 via adigital Input/Output bus 318. The trcv controller 325 is composed of acombination of hardware and software. The trcv controller 325 controlsthe laser modulation control signal 320 and bias control signal 321 viaa signal conversion performed by two Digital to Analog Converters (DAC)319 (though only one shown in figure). The laser modulation and biascontrol signals communicate with the Driver 322 and, thereby, controlthe upper and lower bounds of the output light intensity of the LD 315.This is accomplished by setting upper bounds on lower bounds on thelaser modulation and bias signals provided by the Driver 322 to the LD315. In an alternative embodiment, Driver 322 uses current flow insteadof voltage changes to control laser modulation and bias currents. Thelight transmissions from the LD 315 can be terminated or enabled via thetransmitter disable signal 324, which is an electrical signal sent tothe Driver 322 via the communication logic and memory 131,132.Therefore, in view of the combination of electrical signal(s) 323, lasermodulation control signal(s) 320, laser bias control signal(s) 321 andthe transmitter disable signal(s) 324, the communication logic andmemory 131,132 has control over light transmissions of the transceiver100,101.

With regard to the test methods of the present invention, a transceiverperforming the test methods involving OTDR or OFDR such as ISOTDR,ISOFDR, ISOTDR-ISIL, ISOFDR-ISIL, or ISOTDR-ISOFDR-ISIL test methodsmeasures the reflected test signal or test light transmissions via anoptical receiver such as the PhotoDetector or PhotoDiode (PD) 316. Ingeneral, test signal or test light transmissions from the LD 315 travelinto optical fiber 108 and continually produce reflected light back tothe LD 315 as the test signal or test light transmissions travel alongoptical fiber 108 (e.g., due to Rayleigh scattering, Fresnelreflection). The PD 316 is optimally positioned to receive thesereflected test signal or test light transmissions or reflections. The PD316 is typically referred to as a front facet monitor photo diode thatperforms the function of monitoring the output power of the LD 315. Asdiscussed above, the PD 316 receives the reflected light which it thenconverts to an analog electric signal and transmits this electric signalto the Analog to Digital Converter (ADC) 317. The ADC 317 furtherconverts the analog signal to a digital signal and transmits the digitalsignal to the trcv controller 325. Under the direction of thecommunication logic and memory 131,132, the trcv controller 325 thensends the digital signal, via the digital I/O bus 318, to thecommunication logic and memory 131,132 as the measured OTDR or OFDRdata.

In addition to the above functions, the transceiver 101,100 can alsomeasure test signal or test light transmissions from other opticallylinked transceivers performing the test method involving Insertion Losssuch as the ISIL, ISOTDR-ISIL, ISOFDR-ISIL, or ISOTDR-ISOFDR-ISIL testmethods. These test signal or test light transmissions from the testmethods are measured by the PD 311 and are converted to photocurrentthat is then sent to the TIA 312. The internal circuitry of TIA 312mirrors the average photocurrent and converts this average to aproportional voltage that is often referred to as Receive SenseSensitivity Indicator (RSSI), which is sent to the ADC 317. The ADC 317converts the RSSI signal to digital data that is then sent to the trcvcontroller 325. Under the management of the communication logic andmemory 132,131, the trcv controller 325 then sends the digital data viathe digital I/O bus 318 to the communication logic and memory 132,131 asmeasured ISIL data.

The accuracy of the measurements in accordance with the test methods issignificant to the ultimate usefulness of the results of these testmethods. It will be appreciated that alternative measurement circuitrycan greatly increase the accuracy of the measurements. An exemplaryembodiment of an alternative measurement circuitry is now discussed withreference to FIG. 3. An alternative circuitry involves replacing the PD316 with: a more sensitive PhotoDetector or PhotoDiode (PD) 316 b (e.g.,avalanche photodiode (APD)), a TransImpedance Amplifier (TIA) 316 c anda linear Amplifier (Amp) 316 d. The replacement PD 316 b performs thesame functions as the original PD 316 such as providing photocurrent tothe TIA 316 c. The TIA 316 c converts the photocurrent to an electricalvoltage signal that is then sent to the Amp 316 d. The Amp 316 d, whichcan receive RSSI signals from the TIA 312 as well, provides increasedresolution of these electrical voltage signals to the ADC 317. The restof the process continues as previously discussed. In this regard, theADC 317 converts the electrical voltage signals to digital data that isthen sent to the trcv controller 325. Under the direction of thecommunication logic and memory 131,132, the trcv controller 325 sendsthe digital data to the communication logic and memory 131,132, via thedigital I/O bus 318, as either measured OTDR or OFDR data or measuredISIL data, depending upon the measurement source (e.g., PD 316 b, PD311, respectively).

The transceivers 100,101 shown in FIG. 1A and FIG. 3 are an example ofan embodiment of PLSEs that can be utilized in accordance withdiscussions above. In this regard, a test method request can be receivedvia the (Data IN 1) 115,123 signals or alternatively via some set of(Data IN N) 117,125 signals by the communication logic and memory131,132. The communication logic and memory 131,132, being composed of acombination of hardware and software processes, performs thecoordination of functions required for the execution of the receivedtest method.

After the transceiver 100,101 receives the requested test method and thescheduled time period or frame to perform the test method has arrived,the communication logic and memory 131,132 can transmit information or anotification message, in a format consistent and in synchrony with thenetwork protocol, to notify other linked transceivers 101,100 that therequested test method is being performed. The notification message canalso be used to notify the appropriate capable optical network terminalsof their obligation to measure the requested test method beingperformed. The notification message is transmitted by the communicationlogic and memory 131,132 in accordance and in synchrony with the networkprotocol in-use. Then the communication logic and memory 131,132 usesits control over the LD 315, as previously disclosed, to transmit thetest signal or test light transmissions as prescribed by the test methodparameters of the requested test method.

Following the test signal or test light transmissions, the communicationlogic and memory 131,132 disables further light transmissions from thetransceiver via signal 324. If the requested test method involves OTDRor OFDR measurements such as an ISOTDR, ISOFDR, ISOTDR-ISIL, ISOFDR-ISILor ISOTDR-ISOFDR-ISIL test method, then the communication logic andmemory 131,132 communicates with the trcv controller 325 to receivemeasured OTDR or OFDR data in the manner discussed above. Thecommunication logic and memory 131,132 then records the measurements asprescribed by the test method parameters in memory. If the requestedtest method involves Insertion Loss measurement such as an ISIL testmethod, then the communication logic and memory 131,132 performs norecording of measurements and waits until the end of the duration of themeasurement performed by other linked transceivers. The communicationlogic and memory 131,132 knows the duration of the ISIL test method fromthe test method parameters.

Once the measurement duration has passed, the communication logic andmemory 131,132 can transmit a bit clock recovery sequence or pattern inaccordance and in synchrony with the network protocol in-use. If thetransceiver transmits data signals in continuous mode communication,then the bit clock recovery sequence or pattern is beneficial to restorebit level synchronization with optically linked transceivers. The bitclock recovery sequence or pattern is designed to ensure timing recoveryby the DSR 314. If, however, the transceiver transmits data signals inburst mode communication, then the transceiver can transmit a restoreclock sequence or, alternatively, allow the DSR of linked transceiversto obtain bit level synchronization with the transmissions that are partof the network protocol such as preamble bits from another burst modetransmission. The communication logic and memory 131,132 can convey thestored measurements or results of the test method back to the MSE thatit servers, as per the responsibility of the PLSE via the networkprotocol(s) in-use.

If the transceiver 101,100 receives a notification that an ISOTDR orISOFDR test method is being performed by a linked transceiver, then thecommunication logic and memory 132,131 can ignore any received lighttransmissions or optical data signals for the remaining duration of thetest method. The duration of the test method can be conveyed in thenotification message or can be conveyed by the MSE that this transceiverserves, as per the responsibility of the PLSE, via services of thenetwork protocol. If the test method being performed by the linkedtransceiver involves Insertion Loss measurements such as an ISIL,ISOTDR-ISIL, ISOFDR-ISIL or ISOTDR-ISOFDR-ISIL test method, then thetransceiver is required to measure the test signal or test lighttransmissions as part of the test method. In this regard, thecommunication logic and memory 132,131 communicates to the trcvcontroller 325 to receive measured ISIL data in the manner discussedabove. The communication logic and memory records and stores themeasurements in memory, as prescribed by the test method parameters andfor the duration prescribed by the test method parameters. The pertinentinformation from the test method parameters can be conveyed to thetransceiver 101,100 via a notification message or by the MSE that thistransceiver serves, as per the responsibility of the PLSE, via servicesof the network protocol. After the measurement period and once the DSR314 of the transceiver has achieved bit synchronization, thecommunication logic and memory 131,132 continues receiving optical datasignals from optical fiber input as part of the network protocol in-use.The communication logic and memory 132,131 conveys the storedmeasurements or results of the test method back to the MSE that itservers, as per the responsibility of the PLSE, via the networkprotocol(s) in-use.

It will be appreciated that for WDM, CWDM or DWDM employed in anembodiment of a optical fiber network in accordance with the presentinvention and having a transceiver performing test methods of theinvention as described above, the receive data path of the transceiveris not affected by the test method being performed due to thedifferences in transmit and receive communication wavelengths employedby the network. Likewise, the transmit path of transceivers linked viaoptical fiber to a transceiver performing a test method are not affectedby the test method being performed due to the same differences intransmit and receive communication wavelengths employed by the network.Thus, it will be appreciated that in keeping with the in-service natureof the test methods of the invention a transceiver performing a testmethod of the invention can continue to receive, and linked transceiverscan continue to transmit, network communications in accordance with thenetwork protocol in-use. Furthermore, it will be appreciated that asecond transceiver linked via optical fiber to a first transceiverperforming a first test method can, in lieu of network communications,perform a second test method of the invention that can overlap partiallyor completely in time with the first transceiver performing the firsttest method of the invention due to the use of different wavelengthsused for communication in the different directions between the twotransceivers.

In addition to the previously described optical fiber data network ofFIG. 1A, alternative network configurations are also possible andenvisioned. For example, FIG. 1B illustrates an embodiment of a passiveoptical network (PON), wherein the first transceiver 100 and the secondtransceiver 101 of FIG. 1A correspond to the optical line terminator(OLT) 150 and the optical networking unit (ONU) 155, and/or opticalnetworking terminal (ONT) 160, of FIG. 1B, respectively. PON(s) can beconfigured in either a point-to-point network architecture, wherein oneOLT 150 is connected to one ONT 160 or ONU 155, or a point-to-multipointnetwork architecture, wherein one OLT 150 is connected to a plurality ofONT(s) 160 and/or ONU(s) 155. In one embodiment of a point-to-multipointoptical fiber data network, as shown in FIG. 1B, the OLT 150 is incommunication with multiple ONTs/ONUs 160, 155 via a plurality ofoptical fibers 152. In this regard, optical fiber 152 extendingexternally from the OLT 150 is combined with optical fibers 152extending externally from the ONTs/ONUs 160, 155 by one or more passiveoptical splitters 157. Alternative network configurations, includingalternative embodiments of point-to-multipoint networks are alsopossible.

An embodiment of a PON network in accordance with an embodiment of thepresent invention will now be discussed. As disclosed herein, PONs are ahigh bandwidth point-to-multipoint optical fiber network, which rely onlight-waves for information transfer. Depending on where the PON clientside of the optical fiber terminates, the system can be described as,but not limit to, fiber-to-the-curb (FTTC), fiber-to-the-node (FTTN),fiber-to-the-cell-site (FTTCell) (e.g., cell tower), fiber-to-the-desk(FTTD), fiber-to-the-building (FTTB), fiber-to-the-premise (FTTP), orfiber-to-the-home (FTTH). There exists a master-slave relationshipbetween a PON's OLT and ONT or ONU, respectively, due to the nature ofpoint-to-multipoint systems. In this regard, the OLT is the master ofthe PON, which is the main reason why the OLT usually resides in theService Provider or Network Operator central office or comparable remotehead-end terminal. The central office manages the PON via networkoperations management entities such as Network Operations Center (NOC)entities. The NOC entities exist at the OSI application layer along withother management entities, such as but not limited to NMS, EMS,operations support systems (OSS), and business support systems (BSS)entities, that are used by Service Providers and Network Operators tooperate, administer and manage the PON. Some common NOC managemententity functions known to Service Providers and Network Operators areSubscriber SLA Management, Network Physical Layer Security Management,Fiber Plant Operations Management and Network Procurement Management.All these entities and related network management functions can have abusiness or technical need to access the test method results of thepresent invention. To access these results the entities can makerequests to a peer application layer NCSE entity.

As mentioned previously, NCSEs exchange service requests and test methodresults or measurements with MSEs via the network protocol in-use. In anembodiment of the invention, the network protocol used by the MSE andPLSE is based on or is similar to the International TelecommunicationUnion's (ITU) G.984 Gigabit PON (GPON) and G.987 10 Gigabit PON (XG-PON)protocol series, included herein by reference, as shown in FIG. 4A andFIG. 4B, which is patterned after the OSI model. Alternative exemplarypoint-to-multipoint PON protocol in embodiments include but not limitedto (all included here by reference): IEEE 802.3ah Ethernet PON (EPON),IEEE 802.3av 10 Gigabit Ethernet PON (10G-EPON), WDM-PON, ITU-T G.983(BPON), Data over Cable Service Interface Specification (DOCSIS) PON(D-PON/DPON) and RFoG SCTE IPS910, SCTE 174 2010 as well as any futureaddendum, annex, normative revision or new version of these protocolsfor feature, capability or speed enhancements. Alternative exemplarypoint-to-point optical network protocols in embodiments envisionedinclude but not limited to: Active Ethernet IEEE 802.3ah, GigabitEthernet IEEE 802.3z, 10-Gigabit Ethernet IEEE 802.3ae, 40-GigabitEthernet and 100-Gigabit Ethernet IEEE 802.ba, SONET/SDH as defined byGR-253-CORE from Telcordia and T1.105 from American National StandardsInstitute, Ethernet over SONET/SDH (EoS), Metro Ethernet Forum (MEF)Metro Ethernet, and MPLS based Metro Ethernet as well as any futureaddendum, annex, normative revision or new version of these protocolsfor feature, capability or speed enhancements including NG-PON-2.Exemplary protocols in embodiments used to communicate between an NCSEand an MSE include, but not limited to, network layer protocols such as:IPv4, IPv6, ICMP, OCMPv6, IGMP, and IPsec; and transport layer protocolssuch as: TCP, UDP, DCCP, SCTP, RSVP, and ECN; and application layerprotocols such as BGP, DHCP, DNS, FTP, GTP, HTTP, IMAP, IRC, LDAP, RIP,RTP, RTSP, SIP, SMTP, SNMP, SOAP, SSH, Telnet, TLS/SSL, and XMPP.

Referring now to FIG. 4A which illustrates an OSI reference model andrelated entities for an OLT embodiment and referring to FIG. 4B whichillustrates an OSI reference model and related entities for an ONU/Tembodiment, both based on the GPON protocol and the passing ofinformation between the OSI physical and application layers in exemplaryembodiments of the invention. Between these layers, the PLSE 252, 253resides at the physical layer, the MSE 251,254 resides at the data linklayer, and the NCSE 250,255 resides at the application layer in thisembodiment. As mentioned previously, the interaction between NCSE, MSEand PLSE entities results in a flow of information concerning the testmethods across the network protocol layers.

Referring now to FIG. 4A, OSI Application layer 403A includes ServiceProvider or Network Operator application entities that provide a NOCwith operational, administration and management control over the GPONnetwork and the test methods of present invention. Peer applicationentities that are under a Service Provider or Network Operator controlinclude OLT Administration entity 404, OLT NCSE 440 and OLT DataCommunication entity 450 which are all responsive to an EMS entity andthe EMS entity is responsive to an NMS entity. OLT Administration entity404 performs GPON administration functions outlined byprotocol-independent Management Information Base (MIB) and Fault,Configuration, Accounting, Performance-Monitoring and Security (FCAPS)service functions for an OLT which are defined and administered by theService Provider or Network Operator. OLT Administration entity 404 alsoperforms FCAPS service functions for all client ONU/Ts via anadministration protocol (e.g., SNMP) used by the Service Provider orNetwork Operator to interface 431 with a GPON OLT GTC Adaptation LayerONT management and configuration interface (OMCI) channel adaptationentity 405 for exchanging OMCI messages (e.g., ITU-T G.988 standard,included herein by reference). OLT Administration entity 404 alsoprovides operations, administration, and management, (OAM) servicefunctions over an administration protocol (e.g., SNMP, Telnet, SSH) usedby the Service Provider or Network Operator to interface 432 with a GPONOLT GTC OAM channel adaptation entity 427. OLT NCSE entity 440 isresponsive to NMS, EMS and OLT Administration peer entity 404 throughservice node interface (SNI) 428, SNI as outlined by the GPON standard.OLT NCSE entity 440 processes requests received through SNI 428 toestablish test method parameters, initiate test method events, receivetest method measurements and results, analyze received the test methodmeasurements and results, and issue test method reports and opticalfiber network certification reports. OLT Data Communication entity 450represents data traffic (i.e., data not related to test methods, forexample user application layer data communications).

Referring now to GTC Adaptation Layer 402A and GTC Framing Layer 401Awhich comprise the OSI Data Link layer in this embodiment. GTCAdaptation Layer 402A includes: OMCI Channel Adaptation entity 405 whichprocesses MIB messages from OLT Administration entity 404; VPI/VCIFiltering entity 406 which performs filtering of Virtual PathIdentifiers (VPI) and Virtual Circuit Identifiers (VCI) ATM virtualcircuit for ATM service flows of data and test method communicationsexchanged via ATM Client Access Network Interface entity (ANI) 420 perthe GPON standard; Port-ID Filtering entity 407 which performs filteringof Packet Port-IDs for GEM service flows of data and test methodcommunications via Packet GEM Client User Network Interface-Network sideentity (UNI-N) 421; ATM Cell Adaptation entity 408 which adapts ATMservice flows for encapsulation to the GTC frame per the GPON standard;GEM Packet Adaptation entity 409 which adapts GEM service flows forencapsulation to the GTC frame per the GPON standard; DBA Control entity417A which performs Dynamic Bandwidth Assignment of upstream AllocationIdentifiers (Alloc-ID) used to uniquely identify Transmission Containers(T-CONTs) that multiplex ATM service flows and GEM service flows per theGPON standard; Ethernet Logical Link Control (LLC) and Media AccessControl (MAC) entity 422 which performs protocol multiplexing, flowcontrol, error detection, error control and protocol framing for GEMservice flows per GPON standard, and OAM Channel Adaptation entity 427which conveys GTC frame information such as security exchange, DBA, linkBER monitoring per the GPON standard and conveys test methodinformation. GTC Framing Layer 401A is responsible creating the GTCframe and includes: ATM service flow Alloc-ID Assignment entity 410which performs internal GPON routing functions based on Alloc-ID for ATMservice flows per the GPON standard; GEM service flow Alloc-IDAssignment entity 411 which performs internal GPON routing functionsbased on Alloc-ID for GEM service flows per the GPON standard; ATM CellPartition entity 412 which embeds a portion of the ATM service flow intothe GTC frame per the GPON standard; GEM Packet Partition entity 413which embeds a portion of the GEM service flow into the GTC frame perthe GPON standard; Physical Layer OAM (PLOAM) Partition entity 414 whichembeds a PLOAM message channel into the GTC frame per the GPON standard;PON Frame Header entity 415 which creates and decodes GTC header fieldsresponsive to the Embedded OAM entity 418 per the GPON standard; OLT MSEentity 416A which embeds the test method frame into the GTC frame, as anextension of the GTC frame, responsive to NCSE; Embedded OAM entity 418processes field-formatted information in the header of the GTC framedesigned to provide a low latency path for time urgent controlinformation such as bandwidth granting, key switching, Dynamic BandwidthAssignment signaling, and test method frame processing; and GTC Framingsub-layer entity 419 which multiplexes and de-multiplexes portions ofthe GTC frame responsive to partition entities (e.g., ATM, GEM & PLOAM),PON Header entity 415 and OLT MSE 416A entity to create and manage GTCframe.

The OLT NSCE 440 sends OAM messages to the OLT MSE entity 416A, in theembodiment of FIG. 4A, through OAM Channel Adaptation entity 427 andEmbedded OAM entity 418. OLT MSE 416A receives test method parametersfrom the OAM messages and operates, essentially, as an extension of PONFrame Header entity 415. After receiving test method parameters OLT MSE416A embeds into a portion of a GTC frame a test method frame (discussedfurther below in relation to FIG. 6A). OLT MSE 416A provides the GTCFraming sub-layer 419 the length of the test method frame (e.g., sum ofthe burst time, delay time and test sampling window) and the restoreclock pattern (if used). OLT MSE 416A communicates with and configuresthe OLT PLSE 443A via PMD Control entity 426 to control thetransmissions for OTDR and OFDR test methods which enables test signalsequences or patterns to be transmitted by the OLT and test signalmeasurements to be extracted for OTDR, OFDR or IL tests depending on thetest method.

Referring now to OSI Physical layer 400A which includes OLT PhysicalMedia Dependent (PMD) entity 424A which includes OLT PLSE 443A and PMDcontrol entity 426. OLT PMD entity 424A performs physical layer linecoding functions such as physical layer frame synchronization (e.g.scrambling polynomial), Forward Error Correction (FEC) for bit errordetection or recovery, electrical-to-optical and optical-to-electricalconversion for the transmission and reception of optical communicationsignals. The OLT PLSE 443A is responsible for controlling the OLTtransceiver to perform test light transmission, recording of test lightfor ISIL measurements and recording of reflected test light for OTDR andOFDR measurements. The OLT PLSE 443A manages the behavior andperformance of OLT PMD entity 424A during test method events in responseto OLT MSE 416A.

Referring now to FIG. 4B and optional (discuss further below)Application layer 403B includes ONU/T NCSE entity 480, TechnicianOptical Network Test entity 490, and ONU/T Data Communications 470.ONU/T NCSE entity 480 is a peer entity of the OLT NCSE entity 440 withsimilar capabilities to initiate test methods and is responsive toTechnician Optical Network Test Set entity 490. ONU/T NCSE entity 480provides client side access to test methods via an application layerprotocol (e.g., SNMP) used by network technicians to administer testmethods using Technician Optical Network Test Set entity 490. TechnicianOptical Network Test Set entity 490 is an application entity thatperforms exemplary functions as opening trouble tickets or maintenancetickets, entering test parameters, visualizing test measurements orreports, and closing or signing-off tickets. In some embodimentsTechnician Optical Network Test Set entity 490 can be included in a handheld device separate from the ONU/T or in alternative embodimentsembedded with an ONU/T. In yet another alternative, yet similar,embodiment, technicians can gain access to OLT NCSE entity 440 or ONU/TNCSE entity 480 via communication methods such as cellular 3G, 4G or LTEwireless network, in conjunction with using the Service Provider orNetwork Operator OSS and BSS platform services which allows thetechnician access to the appropriate NMS or EMS communications forinitiating test methods. These embodiments are beneficial to techniciansand optical fiber plant operations and administrations management toglean the most amount of information about the state of the opticalfiber link while in remote locations outside NOC and Service Provider orNetwork operator facilities. However, it will be appreciated that ONU/TNCSE entity 480 and Technician Optical Network test entity 490 areoptional in terms of performing test methods and need not be in allembodiments, only embodiments where initiating test methods or obtainingtest method results directly from an ONU/T client or remotely from anOLT is desired. ONU/T Data Communication entity 470 represents normaldata traffic (i.e., data not related to test methods, for example userapplication layer data communications).

Referring now to GTC Adaptation Layer 402B and GTC Framing Layer 401Bwhich comprise similar entities that performs similar functions aspreviously describe in relation to GTC Adaptation Layer 402A and GTCFraming Layer 401A. ONU/T MSE entity 416B is a peer entity of OLT MSEentity 416A and performs similar functions to OLT MSE entity 416A aspreviously discussed. ONU/T MSE entity 416B responds to OLT NCSE 440 anddepending on the embodiment may also respond to ONU/T NCSE entity 480 byreceiving OAM messages through Embedded OAM entity 418. It will beappreciated that OAM messages from OLT NCSE 440 to ONU/T MSE entity 416Bare transferred via OMCI Channel Adaptation entity 405 and received byONU/T Physical Media Dependent (PMD) layer entity 424B and pass througheither PLOAM Partition 414 or PON Frame Header entity 415 to EmbeddedOAM entity 418 of the ONU/T. It will also be appreciated that ONU/T MSEentity 416B passes the length of the test method (e.g., sum of the bursttime, delay time and test sampling window) to DBA Control entity 417Bwhich sends bandwidth requests and status of queues upstream to DBAControl entity 417A and DBA Control entity 417A allocates or schedulesbandwidth with a unique identifier (e.g., ALLOC-ID) to perform theupstream test method and sends the allocation information (e.g.,upstream bandwidth map) to the ONU/T per the GPON protocol. It will beappreciated that in some embodiments DBA Control entity 417A canmaintain quality of service for ATM and GEM service flows concurrentwith test method events.

Referring now to OSI Physical layer 400B which performs similar butcomplementary functions to OSI Physical layer 400A and includes ONU/TPMD layer entity 424B which in turn includes ONU/T PLSE 443B and PMDcontrol entity 426. It will be appreciated that while ONU/T PMD layerentity 424B and ONU/T PLSE 443B perform similar but complementaryfunctions to OLT PMD layer entity 424A and OLT PLSE 443A, respectively,as previously discussed, ONU/T clients transmit and receive on differentwavelengths to the OLT and ONU/T clients perform burst modetransmission. The OLT PLSE 443A and ONU/T PLSE 443B control the GPON PMDoptical transceiver responsive to respective MSEs 416A,416B and insynchrony with the GTC Framing sub-layer entity 419, thereby ensuringtest methods can occur while maintaining the continuity of network datacommunication and services across the PON.

It will be appreciated that alternative embodiments of FIG. 4A and FIG.4B employing ITU-T G.987 XG-PON protocol are not only possible butenvisioned. It will be appreciated that alternative embodiments of FIG.4A and FIG. 4B that arrange or combine entities and functionsdifferently than shown or discussed are possible.

In some embodiments, test methods may cause receivers of opticalterminals on the PON to lose frame synchronization. For example, a testmethod in the downstream that spans more than one GPON frame. In someembodiments this can require circuitry within the physical layer toensure proper management and synchronization of the bit clocks aremaintained to prevent false loss of clock events, which may cause falseframe-synchronization error events on the PON. A description of anembodiment of the physical circuitry is discussed in further detailbelow in reference to FIG. 5. In alternative embodiments false framesynchronization error events triggered by test methods can simply beignored safely when an OLT or ONU/T has knowledge a test method isoccurring or had occurred. In yet another alternative embodimentadditional frame synchronization bits or clock bits can follow the testmethods event.

A functional block diagram of the physical block level circuitry andphysical and data link layer for exemplary ITU-T GPON PON or G.987XG-PON OLT 500 and ONU/T 501 embodiments are disclosed with reference toFIG. 5. Physical Layer 508,509 consists of the optical transceivers504,505 along with clock and data recovery (CDR) functionality 510,511.Non-correlated electrical receive energy from the optical transceivers504,505, created by GPON and XG-PON scrambling polynomial framesynchronization process to limit consecutive identical digits, is usedas inputs to the CDR 512,513. The OLT receive path 512 is a burst modetype consequently a burst mode (BM) CDR 510 is used; whereas the ONU/Treceive path 513 is a continuous mode type and consequently a continuousmode (CM) CDR 511 is used. In some embodiments, an early indication thata burst is pending can be sent or generated to facilitate and simplifyBM CDR 510 bias control circuitry by the OLT GTC Adaptation and FrameProcessing block 535 referenced as a Pre-Burst (Pre-B) Indicator signal519.

As shown in FIG. 5, the DATA Link Layer 514,515 functions to processincoming receive data (RXD) 517,538, which is synchronized with thereceiver clock (RXCLK) 518,539 by the BM CDR 510 or CM CDR 511respectively, and to process outgoing transmit data (TXD) 516,537. BothOLT and ONU/Ts MSE blocks 526,546 are responsive to an OLT NCSE (notshown) as well as MIB management functions via OAM and OMCI informationexchange for initiating test methods as previously discussed. The OLTGTC Framing process 535 performs all the downstream and upstream byteand bit level formatting of information as well as generating thePre-Burst (Pre-B) 519 signal. This downstream and upstream byte or bitlevel formatting is shown in FIG. 6 and FIG. 7 and discussed in furtherdetail below. The OLT PLSE block 527 is responsive to the OLT MSE block526 and manages several event indicators, such as managing the PMDcontrol block 524, and masks or gates 533,532 the Loss of Bit Lock(LOL_(bit)) 520 and Loss of Bit Signal (LOS_(bit)) 521.

Additionally, in embodiments of the invention utilizing an APD, a PLSEcan generate a pre-charge APD signal that generates an APD bias voltagefor an APD, in optical transceiver used for OTDR and OFDR measurements(i.e., reflections of the test signal) to more quickly establish thegain or sensitivity of the APD and to save power. Furthermore inembodiments of the invention utilizing an APD, the pre-charge APD signalcan be inversely related to the transmitter disable or transmitter laseroff (TX Laser Off) signal which turns of the transmitter (e.g. laserdiode) during test methods (e.g., during measurement period or samplingwindow of a test method). For example, when the transmitter is turningoff, the APD is turning on, and while the output of the transmitterfades out the bias voltage across the APD is being established. By usingthe transmitter disable signal for the pre-charge APD signal, themaximum sensitivity of an APD based receive-reflection circuitry can beachieved in the shortest time. Fast reflection measurement acquisitiontimes can be achieved in these embodiments, which can reduce the DelayTime (DT) period 627 of a test method frame. This can improve OTDR andOFDR performance of embodiments by increasing the near field distancefrom the transmitter where reflection of transmitted test signals can bemeasured with reasonable accuracy. Additionally, receive sensitivitymeasurements of −48 dB or better from reflected test signal(s) can beachieved with these embodiments, which extends the reach or distance ofwhere measurements can be taken with reasonable accuracy. In alternativeembodiments, the bias voltage of the APD is always maintained afterstartup of the optical transceiver. It will be appreciated that in someembodiments the APD bias voltage may be compensated to account fortemperature and the manufacturing process used to manufacture the APD inorder to achieve a constant gain or receive sensitivity.

To minimize the impact to OLT services provided across a GPON andXG-PON, in some embodiments, it is beneficial for OLT MSE and PLSE togate 532,533 BM CDR state indicator signals (i.e., LOL_(bit) 520 andLOS_(bit) 521) so that bit error management or frame synchronizationroutines are not falsely triggered during test method events. Byensuring proper masking of these BM CDR state indicator bits 520,521, atest method can occur while maintaining synchrony and continuity ofnetwork communications and services deployed across a GPON or XG-PON. Byproperly coordinating events in accordance and in synchrony with thenetwork protocol in-use the OLT MSE block 526 can ensure a test methodis performed while network data communications, or services areprocessed by the OLT GTC Adaptation and Framing Processing block 535ensuring continuity of data communications is maintained. Eventmanagement is important to enabling test methods using the sametransceivers 504,505 used for the network data communication. Properevent management in accordance and in synchrony with the networkprotocol having predetermined time intervals or frames for datacommunications is discussed further below.

Referring to FIG. 5, on the ONU or ONT client or multipoint subscriberside of a PON system, similar event coordination by the ONU/T MSE block546 is required to perform test methods. The ONU/T Physical Layer andData Link Layer sub-systems shown in FIG. 5 include a similar set offunctions found on the OLT to perform test methods. The ONU/T MSE block546 coordinates events between the ONU/T GTC Adaptation and FramingProcessing block 554, the ONU/T PLSE block 555 and the PMD control 544.The ONU/T GTC Adaptation and Frame Processing block 554 performs similarfunctions as the OLT Framing Processing block 535. The main differenceis on the client or multipoint side, burst and continuous mode ofoperations are reversed. In this regard, the ONU/T's transmit path (TXD)537 behaves in a burst mode fashion with a Pre-Burst (Pre-B) indicatorsignal 536 controlling the behavior of the Upstream burst. The ONU/T'sreceive path is characterized by the receive data stream (RXD) 538 andrecovered receive clock (RXCLK) 539. Some embodiments may performpre-charging of an APD in transceiver 505 as previously discussed. Inaddition as previously discussed, inputs from the ONU/T's CDR bit states540,541 may trigger false resynchronization events during test methods.The LOL_(bit) 540 and LOS_(bit) 541 indicators and gating mechanism551,552 are under the control of the ONU/T PLSE block 555, similar tothe OLT's PLSE block 527. The source clock signal from the ONU/T CM CDR511 generates the Loss of bit Lock (LOLbit) 540 and Loss of bit Signal(LOSbit) 541 signals and the ONU/T PLSE block 555 controls the LOLbitgate 551 and LOSbit gate 552 for the LOLbit 540 and LOSbit 541 signals.In summary, by coordinating the masking or gating of the ONU/T CM CDR511 state indicators 540 and 541, the ONU/T PLSE block 555 can performtest methods while maintaining synchrony and continuity of GTC framesynchronization required to maintain network data communications orservices, as discussed further below.

FIG. 6A illustrates an exemplary embodiment of a diagrammaticrepresentation of the downstream network protocol having predeterminedtime intervals or frames for data communications (e.g., PON GTC FrameInterval 605) which includes the multiplexing and framing of informationin a point-to-multipoint GPON PON system. The term downstream is meantto indicate information that originates at the OLT and terminates at anONU/T. In general, the downstream GPON Transmission Convergence (GTC)frames 600 include a series of consecutive GTC header sections 603 pluspayload frame sections 604. The GTC downstream header is referred to asthe Physical Control Block Downstream (PCBd) 603 and can includePhysical Synchronization (PSync) field 610, which is a fixed 32-bitpattern used by an ONU/T to synchronize to the beginning of the GTCframe; GTC Frame Identification field (Ident) 611, which includes a30-bit superframe counter; Physical Layer OAM downstream (PLOAMd) 612,which is used to send PLOAM message to an ONU/T; Bit Interleaved Parity(BIP) field 613, which is used by an ONU/T to determine the downstreamBit Error Rate (BER); Payload Length downstream (PLend) field 614, whichis transmitted twice for robust error detection and includes a two12-bit field used to convey the length of the upstream bandwidth map andlength of the ATM partition; and the Upstream Bandwidth Map (US BW Map)615 fields, which contains a scalar array of 8-byte allocationstructures used by an ONU/T to determine when it can transmit. Inalternative embodiments, some fields can be omitted, extra fields addedand/or the field order altered.

Either ATM cells or GPON Encapsulation Method (GEM) packets can beincluded in the Payload Frame section 604 section. Each GTC downstreamframe have a fixed frame interval 605 however the number (e.g., K) ofATM cells 606 or the number (e.g., J) of frame fragments over GEM 607can vary. Within a GEM frame 607 of the GTC Payload Frame 604, aconsecutive series 609 of GEM header 616 and GEM payload 617 segmentsare aligned to fill an entire GTC frame segment 607. Typically, GEMframe 607 is sent before the start of the next PON frame, which is areason why the start of a GTC header or PCBd 603 begins with a PSync610. Repeating the PSync 610 in a predictable manner (e.g., having arecurring GTC frame interval of eight kilohertz) ensures proper GTCframe lock is maintained.

In general, test methods adhere to and support a predictable GTC PONframe alignment method. By taking advantage of the last GEM payloadbefore the beginning of the following PCBd 603, a test method can beperformed in a manner that maintains the continuity of the PON frame andnetwork communications or services wherein the GEM payload 602(comprising several time intervals or sub-frames 624-629) serves as atest interval to perform a test method in continuous mode or downstreamcommunications. In some embodiments, to schedule and to insure properidentification of a pending test method, a special test method typefield 624 is used to inform all ONU/Ts of the pending test method.Normally this Type field 623 is used to identify the type of PayloadData Unit (PDU) 621. Once the ONU/T receives a test method indication,then the ONU/T masks Loss of Bit Lock (LOL_(bit)) 631 and Loss of BitSignal (LOS_(bit)) 632 to prevent false resynchronization events.Additionally in some embodiments to ensure proper synchronization ismaintained, the ONU/T's CDR can be given a pre-restore bit clock pulseindicator 633 that allows the CDR circuitry to normalize bias circuitryand establish a faster bit clock time and data lock time. Furthermore,the ONU/T's CDR require a good clock source in the data stream torestore the bit clock and in some embodiments providing a series ofalternating 0s and 1s within a Restore Clock 629 field or an alternativebit sequence or pattern can ensure the bit clock and data recovery isachieved. The unmasking of the LOL_(bit) 631 and LOS_(bit) 632 can betriggered after the ONU/T's CDR 634 establishes lock on Restore Clock629 or similar reference data. Once both ONU/T CDR state indicator bits(i.e., LOL_(bit) 631 and LOS_(bit) 632) have established phase andsignal lock, then the PON framing processing block can begin the GTCframe synchronization hunt or search which marks the earliest time thisHUNT state 636 (e.g., early start of GEM header HEC hunt, Pre-Sync andSync state delineation process) can be performed in some embodiments.

The sampling and recording of measurements of a test method can occurduring or after the configured In-Service (IS) Burst 626 (whichrepresents a period for the test signal transmission) and Delay Time(DT) 627 (which represents the of period time between the transmitterturning off and having no light being emitted from the transmitter) havepassed from the perspective of an optical transmitter or while it occursfrom the perspective of an optical receiver. DT 627 is optional in testmethods and need not appear in all embodiments of the invention. Byvarying desired intensity and frequency characteristics (frequencydiscussed further below) of the IS Burst 626 optical transmission testsignal various optical fiber link diagnostics techniques can beperformed such as, but not limited to, optical time domainreflectrometry (OTDR), insertion loss, and optical frequency domainreflectrometry (OFDR). Regardless of the optical fiber plant diagnosticstechnique used, multiple test method results or measurements frommultiple tests can be used to perform statistical analysis or create anaveraged representation of all impairments across the optical fibernetwork.

It will be appreciated that the duration or interval of a test methodcan last longer than a single GTC frame interval (e.g., duration ofthree GTC frame intervals of 125 μs is possible for a 20 km fiber link).However, in downstream communications in both GPON and XG-PON protocols,the ONU/T clients expect to see downstream frame synchronization fields(e.g., PSync 610) at every GTC frame interval (i.e., every 125 μs). Amethod to schedule and extend test methods beyond a predetermined fixedframe interval of a communication protocol is now disclosed wherein bitfields in the header are used to indicate the duration (e.g., how manyframes) of a test method. For example in GPON and XG-PON using GEM, thepayload length indicator (PLI) field 618 in the GEM Header 616 indicatesthe length, in bytes, of the succeeding GEM Payload fragment 617 and isused to delineate and find the next header in the stream and tocontributes to the determination of the end of the GTC frame interval.The payload typed indicator (PTI) field 638 is used to indicate thecontent type of the GEM Payload fragment 617 (e.g., user data, OAM) andindicates if it is the last fragment of the content type. The PTI field638 values are shown in the table of FIG. 6B, the PTI field 638 is a3-bit field indicator with reserved values. In an embodiment of theinvention, a reserved PTI field 638 code value (e.g., 111) is used toindicate that a test method will begin in the succeeding GEM payloadfragment 617 and to check the GEM frame fragment header 620 for testmethod type field 624 and for an extension of the PLI field (xPLId) 625which can be used to indicate the length of the test method (e.g.,length in bytes). Use of the test method type filed 624 providesidentification of the test method type (e.g., ISOTDR, ISOFDR, ISIL,ISOTDR-ISIL, ISOFDR-ISIL, and ISOTDR-ISOFDR-ISIL) and the xPLId 625provides the duration of the test method (e.g., PLI plus xPLId fieldsprovide a measure in bytes to the first byte of the succeeding GEM frameafter the test method).

Referring now to FIG. 6C, an exemplary method of incorporatingin-service diagnostic or test methods in the downstream communicationsof ITU G.984 GPON or ITU G.987 XG-PON protocols in view of previousdiscussions and in view of FIGS. 4A-6B is summarized. Starting withrequesting a downstream test method 680, by a peer application entity(e.g., EMS, NMS), to be performed between the OLT and an ONU/T the OLTNCSE (e.g., OLT NCSE 440) initiates a downstream test method responsiveto the request. The OLT NCSE then processes the request to establishtest method parameters (e.g., ONU/T address, test type, test signalfrequency or pattern, sampling rate) and initiates the test method bysending, for example, an OAM message through OAM Channel Adaptationentity 427 and Embedded OAM entity 418 to OLT MSE (e.g., OLT MSE 416A).The OLT MSE, responsive to the message received from the NCSE, thencauses the generation of a test method frame 682 (i.e., as representedby 602 of FIG. 6A) by the GTC Framing sub-layer entity 419 including thetest method type field 624, xPLId fields 625 and Port-ID (which can beused to identify an ONU/T to perform insertion loss measurementdepending on the test method) and signaling the OLT PLSE (e.g., OLT PLSE443A) to manage the OLT transceiver for test signal transmission andrecording of test signal measurements (for test involving OTDR or OFDR).After the test method event, ONU/Ts search for GEM headers or PSyncs anddownstream communications continues 684 having maintained synchrony andcontinuity of downstream communication flows through the test methodevent. Test method results are sent 686 either through OAM messages(from OLT MSE) or through PLOAM (from ONU/T MSE) to the OLT NCSE.

It will be appreciated that test methods can be given unique trafficidentifiers, such as an Alloc-ID 639 and Port-ID 637. An exemplarymethod of associating an Alloc-ID with test methods in embodiments ofthe invention is using PLOAM. Referring now to FIG. 6D which illustratesthe format of PLOAM messages 690 in GPON and XG-PON protocols. PLOAMmessages 690 comprise: an ONU ID field used to address a specific ONU/Tand used to broadcast to all ONU/Ts, a Message ID field used to indicatethe type of message, a data field for the payload of the message and aCRC field covering the previous fields. A PLOAM message for assigning anAlloc-ID to test methods 692 comprises of: addressing the PLOAM messageto an ONU/T, using the message type identifier for assigning Alloc-IDs(e.g., 00001010 as per GPON and XG-PON protocol specification), theunique Alloc-ID to be associated with the test methods and a payloadtype field using a reserved payload type value (e.g., 0x3) to indicatethat the payload is associated with test methods. Alternatively, aunique Alloc-ID can be given to each type of test method as well as aunique Alloc-ID to send test method results. Once an Alloc-ID isassociated with a test method another PLOAM message can be used toconfigure the test method and associate the test method with a Port-ID.For example, a PLOAM message for configuring test methods based onPort-IDs 694 comprises of: an address for the ONU/T, test method messagetype indicator, the Port-ID associated with test method and the testmethod configuration payload. The test method configuration payloadfield can comprise of bit field indicators to indicate the type of test(e.g., ISOTDR, ISOFDR, ISIL, ISOTDR-ISIL, ISOFDR-ISIL, andISOTDR-ISOFDR-ISIL), the method to use to report the results (e.g.,through PLOAMu, OMCI, or GEM), the length of the test signal burst,length of the delay time period, and other test method parameters (e.g.,test signal frequency or pattern, sampling rate and resolution) aspreviously mentioned.

Test methods scheduled to be performed in the upstream can be allocatedor granted a specific window of time to perform the test method. Amethod to perform the allocation is to send the allocation as part ofthe normal upstream allocations in the US BW Map 615. The US BWallocation structure comprises of: the Alloc-ID 639 associated with theallocation, a flag field 640, and start 641 and stop time 642 fieldswhich indicate the start and stop time of the allocation in bytesrelative to the beginning of the upstream frame. Referring now to FIG.6E, an exemplary embodiment of an US BW map allocation for a test methodis illustrated that uses reserved bits in the US BW flag field 640 toconvey whether the stop time 642 of the allocation is relative to thebeginning of the upstream frame in which the test method began orwhether the stop time 642 of the allocation is relative to the beginningof the next upstream frame or relative to the next consecutive upstreamframe. Alternative embodiments can use more reserved bits to extend thestop time to be relative to the beginning of even more subsequentupstream frames.

Referring now to FIG. 7A which illustrates an embodiment of adiagrammatic representation of the upstream network protocol havingpredetermined time intervals or frames for data communications (e.g., USVirtual Frame TX Interval 702) which includes the multiplexing andframing of information in a point-to-multipoint GPON PON system. Theterm upstream is meant to indicate information that originates at theONU/T and terminates at an OLT. Since the upstream is shared by allONU/Ts, the upstream is usually divided into slots 700, with each ONU/Tsending information over OLT assigned slots in an upstream GTC frame705. An upstream frame interval 702 can include information from aplurality of ONU/Ts. Since each ONU/T only sends data for a period oftime, it is said to burst data and is differentiated from the downstreamcontinuous mode.

The GTC downstream header is referred to as the Physical Control BlockUpstream (PCBu) 703 and can include fields of data that convey thefollowing: Physical Layer Overhead Upstream (PLOu) 717, Physical LayerOAM upstream (PLOAMu) 718, Power Leveling Sequence upstream (PLSu) 719,and Dynamic Bandwidth Reporting upstream (DBAu) 720. PLOu 717 includes:preamble and delimiter used for synchronization and identification tothe GTC upstream frame; Bit Interleave parity used by the OLT todetermine upstream BER; ONU-ID used to identify the transmitting ONU/T,and Indication field (Ind) used to support real-time ONU status to theOLT. The PLOAMu 718 is used to send PLOAM messages to the OLT. The PLSu719 can be used to adjust the ONU/T power levels and thereby reduce theoptical power dynamic range seen by OLT 722. DBAu 720 provides a way foran ONU to send a DBA report on any and all of its T-CONTs in a singletransmission. Some fields can be omitted, extra fields added or thefield order altered. Either ATM cells or GEM Packets can be included inthe GTC Burst Payload 704. Each PON GTC upstream frame can include afixed or variable frame interval 705 and the number of ATM cells or GEMpackets can vary as well. Within the GTC Burst Payload 704, aconsecutive series of GEM packet header and GEM packet payload segments706 are aligned to fill the entire GTC Burst Payload segment 704.

Test methods adhere to and support the framing methods in accordance andin synchrony with the upstream network protocol. For example, by takingadvantage of the last GEM payload of the GTC Burst Payload 716, a testmethod can be performed wherein a GEM payload or frame 716 serves as apredetermined time interval to perform a test method in burst mode orupstream communications. To insure proper identification of a pendingtest method, a test method type field 624 can be used to identify thetest method being performed. Once the OLT receives a test methodnotification, then the OLT can mask the Loss of Bit Lock (LOL_(bit)) andLoss of Bit Signal (LOS_(bit)) 710 to prevent false resynchronizationevents. The unmasking of LOL_(bit) and LOS_(bit) can be triggered afterthe ONU/T has finished transmitting during the Silence period 711 andbefore another burst transmission by another ONU/T. The silence periodis one or more unassigned slots and allows time for the burst mode CDRbias circuitry to reset for the next PCBu. Clock recovery is obtained inthe normal PON process with the next PCBu 712.

The recording of measurements of a test method occurs after theconfigured IS Burst 626 and Delay Time (DT) 627 have passed from theperspective of an optical transmitter or while it occurs from theperspective of an optical receiver, similar to the downstream case(again DT 627 is optional). By varying desired intensity and frequencycharacteristics (frequency discussed further below) of the IS Burst 626optical transmission signal various optical fiber plant diagnosticstechniques can be performed such as, but not limited to, OTDR, InsertionLoss and OFDR. Regardless of the optical fiber plant diagnosticstechnique used, multiple test method results or measurements frommultiple tests can be used to create an averaged representation of allimpairments across the optical fiber network. It will be appreciatedthat this average can also be correlated with test method measurementsfrom more than one wavelength (such as the combination of downstream andupstream measurements or results) on the optical fiber network tofurther improve representation of all impairments and their location ordistance from the optical network terminals.

It will be appreciated that test method results can be sent throughPLOAM, OMCI or GEM, as previously mentioned. Referring now to FIG. 7B,which illustrates an embodiment of a PLOAM message being used to conveytest method results. The PLOAM message comprises, as previouslydiscussed, the ONU-ID field to identify the ONU-ID originating the testmethod results, a message type indicator indicating the PLOAM isassociated with test methods, a Port-ID associated with the test method,and the PLOAM payload field can be filed with test method results.Additional PLOAM messages can be sent to convey test method results thatspan more than a single PLOAM payload field can. OMCI messages aresimilar to PLOAM messages. GEM can be used for example by encapsulatingEthernet frames containing test method results in the payload with GEMas represented by figure elements 645 and 745 in FIG. 6A and FIG. 7A,respectively

Referring now to FIG. 7C, an exemplary method of incorporatingin-service diagnostic or test methods in the upstream communications ofITU G.984 GPON or ITU G.987 XG-PON protocols in view of previousdiscussions and in view of FIGS. 4A-7B is summarized. Starting withrequesting an upstream test method 780, by a peer application entity(e.g., EMS, NMS), to be performed between an ONU/T and the OLT the OLTNCSE (e.g., OLT NCSE 440) initiates a downstream test method responsiveto the request. The OLT NCSE then processes the request to establishtest method parameters (e.g., ONU/T address, test type, test signalfrequency or pattern, sampling rate) and initiates the test method bysending, for example, an PLOAM message through OAM Channel Adaptationentity 427, Embedded OAM entity 418 and PLOAM partition entity 414 toONU/T MSE (e.g., ONU/T MSE 416B). The PLOAM message configures the ONU/Tto perform the test method (e.g., type of test method, length of testsignal burst, length of delay time period, test signal frequency orpattern). The OLT NCSE then sends an OAM message to the DBA controlentity 417A which schedules and generates an allocation in the US BW mapfor the ONU/T to perform the test method. The test method allocation isthen sent to the ONU/T 784. The ONU/T MSE, responsive to the PLOAM andallocation messages received from the OLT, then causes the generation ofa test method frame 786 (i.e., as represented by 706 of FIG. 7A) at theallocated time including the test method type field 624, xPLId fields625 and Port-ID (which identifies the ONU/T performing the test method)and signaling the ONU/T PLSE (e.g., ONU/T PLSE 443B) to manage the ONU/Ttransceiver for test signal transmission and recording of test signalmeasurements (for test involving OTDR or OFDR). After the test methodevent, upstream communications continues having maintained synchrony andcontinuity of upstream communication flows through the test methodevent. Test method results are sent 788 either through OAM messages(from OLT MSE) or through PLOAM, OMCI or GEM (from ONU/T MSE) to the OLTNCSE as previously discussed. It will be appreciated in an alternativeembodiment, Port-IDs for each test method type can be assigned andpre-configured and therefore eliminate the need of sending a PLOAMmessage 782 for configuring the ONU/T to perform the test method.

In alternate embodiments in accordance with the present invention ofpoint-to-point WDM, CWDM, or DWDM optical fiber networks employing thetest methods both downstream and upstream data communications canoperate in a continuous mode. This implies that point-to-point systemssupporting test methods behave in a similar manner to the downstreamdirection of point-to-multipoint systems. Additionally, if thepoint-to-point line codes use control symbol characters to escape fromnetwork data communications transfer operations, then a new controlsymbol character can be used to multiplex a test method into the networkdata communications of a point-to-point system thereby enabling testmethods to be performed in accordance and in synchrony with thepoint-to-point network protocol in-use. A similar test method packet 602can be used in both directions for a point-to-point link. In general,the control symbol character is similar in function to a downstreampacket header, as described herein for point-to-multipoint systems. Inaddition, all the processing of events described herein for thedownstream direction of point-to-multipoint systems are also needed inpoint-to-point systems.

In some embodiments results from test methods can be stored remotely,with respect to the optical network terminals (e.g., an externalserver), and administered by a Service Provider or a Network Operator.In addition, the ONU/T's test method results can be stored locally inthe ONU/T equipment for comparison use by maintenance personnel ineither point-to-point or point-to-multipoint systems. In addition itwill be appreciated that Service Providers or Network Operators can usetest method reports to optimally dispatch maintenance personnel andequipment. The financial benefits to Service Providers or NetworkOperators attributed to the test methods as described herein can besubstantial.

Referring now to the exemplary embodiment of an optical network terminalof FIG. 8 in view of FIG. 3, whereas FIG. 3 illustrated PD 316 b, TIA316 c, Amp 316 d, ADC 317 as part of optical transmitter Tx 134/135,FIG. 8 illustrates an alternative embodiment of the invention with PD316 b, TIA 316 c, Amp 316 d, ADC 317 as part of optical receiver Rx133/136 subsystem. Depending upon the implementation of fiber opticinterface 301, FIG. 8 can provide a more accurate measurement of lightbackscattered from the front facet of the transceiver. Tx 135/135 canstill have a monitor photodiode mPD 816 and associated TIA 816 c, Amp816 d and ADC 817 to monitor and control the output power of LD 315 overvarious operating conditions and over time. It will be appreciated thatwhile photodiodes 316, 316 b and 816 have been shown with associatedamplifiers, in an alternative embodiment photodiodes 316, 316 b and 816can produce a signal that needs no further amplification. Additionally,it will be appreciated that while signals from photodiode PD 311 havebeen shown to share Amp 316 d and ADC 317, in an alternative embodimentthis need not be the case and signals from PD 311 can have their ownamplifier and analog-to-digital converter. Furthermore in someembodiments, amplification or analog-to-digital conversion of signalsfrom PD 311 or PD 316, 316 b can be implemented by DSR 314.

It will be appreciated that the photodiode PD 316 b in FIG. 8 canmeasure the optical return loss of the optical transmitter Tx 134/135.Optical return loss (ORL) is a ratio (P_(r)/P_(t)) representing theoptical power reflected (P_(r)) from a transmitted optical wave (P_(t)).As previously mentioned PD 316 b is capable of measuring reflected light(P_(r)) received from optical fiber 108 and optical interface 301.Additionally, mPD 816 in FIG. 8 as a monitor photodiode can measure thetransmitted optical output (P_(t)) of LD 315. Thus ORL can be calculatedfrom measured P_(r) and P_(t) values and in addition to the results ofan insertion loss test, the required increase or decrease in transmittedoptical power by LD 315 to achieve a desired received optical power atan optical receiver across optical fiber 108 can be determined.

It will be appreciated that the transceivers of FIG. 3 and FIG. 8 canperform OTDR measurements from the optical backscatter when burst modenetwork communications are used, such as the upstream communicationsfrom a ONTs or ONUs 160, 155 on a PON (FIG. 1B). In burst modecommunications there are silence periods 711 in between data signalbursts, see FIG. 7. These silence periods can be used as samplingwindows to measure optical reflections from either a desired OTDR signaltransmitted by transceiver 100 or 101 during the silence period or byusing the trail end of network data signal communications transmitted bytransceiver 100 or 101 prior to the silence period. Measurements can beprocessed and sent to an NCSE or a peer NCSE as per the test methods ofthe invention previously discussed.

It will be appreciated that embodiments of the invention can perform anOFDR test, as previously discussed. Referring now to FIG. 3 and FIG. 8,during OFDR test methods DAC 319 and Driver 322 can generate anappropriate modulation current which in turn produces an optical carrierwith a linear periodic frequency sweep from LD 315 and measurements ofthe received response can be performed by PD 316 or PD 316 b. Given thedata rates for data communications in the gigabits per second areenvisioned, an optical carrier signal on a communication wavelength inthe gigahertz can be produced yielding spacial resolutions in thecentimeters. In addition, alternative embodiments of FIG. 3 and FIG. 8can employ direct digital synthesis (DDS) for improved high frequencyoptical carrier signal generation are envisioned (not shown in figures).DAC 319 with the addition of a numerically-controlled oscillator (NCO)can be used to create a DDS, though alternative methods well known inthe art (including a software based NCO) can also be employed to createa DDS.

Additionally, processing of the received OFDR response can occur at thenetwork terminal performing the OFDR or the received responsemeasurements can be transmitted via the network protocol in-use (e.g.,as payload data) to an external location (e.g., a network server) forprocessing (i.e., inverse Fourier transform). Furthermore, measuredresults from any test method disclosed can be transmitted via thenetwork protocol in-use (e.g., as payload data) to an external location(e.g., a network server) for processing and archiving.

It will be further appreciated that while the test methods of theinvention can scale to provide in-service test services for ServiceProviders and Network Operators to manage their entire optical fiberplants from a single NOC or multiple distributed NOCs, the invention canalso scale to any large or small optical fiber network without a NOC.For example, in one embodiment for an optical fiber network without aNOC and wherein the NCSE (embedded within an optical network terminal orapparatus) is configured to perform embedded OTDR, OFDR, or InsertionLoss tests at some predefined interval(s), or at a communicationdisruption event, or during silence periods in burst modecommunications, or additionally in lieu of idle packets in continuousmode communications as exemplary conditions for initiating a testmethod. The optical network terminal or apparatus can then perform thetest method via embedded MSE and PLSE as previously discussed. Anexample of an optical fiber network without a NOC is an optical localarea network (LAN).

Referring now to FIG. 9A and FIG. 9B, in view of FIG. 4A and FIG. 4B,exemplary embodiments of an OSI reference model and related entities foran OLT and ONU/T, respectively, of the invention for IEEE 802.3Point-to-Point Ethernet optical fiber networks such as those based onIEEE 802.3z GE protocol, IEEE 802.3ae 10GE protocol, or IEEE 802.3ahactive Ethernet protocol or for SONET ring networks are shown. FIG. 9Aand FIG. 9B illustrates how the IEEE 802.3 protocol series can pass bothdata and test method information between the OSI physical layer andapplication layer entities. Between these layers, the PLSE 252,253resides at the physical layer, the MSE 251,254 resides at the data linklayer, and the NCSE 250,255 resides at the application layer in thisembodiment. As previously mentioned, the interaction between NCSE, MSEand PLSE entities results in a flow of information concerning the testmethods performed on the ODN across the IEEE 802.3 network protocollayers.

IEEE 802.3 Physical Layer 900 is comprised of Reconciliation Sub-layer(RS) entity 920, Physical Coding Sub-layer (PCS) entity 922 withoptional Wide area network (WAN) Interface Sub-layer (WIS) entity,Physical Medium Attachment (PMA) sub-layer entity 923, OLT PhysicalMedia Dependent (PMD) sub-layer entity 924A comprising OLT PLSE 443A,and ONU/T PMD sub-layer entity 924B comprising ONU/T PLSE 443B. It willbe appreciated that OLT PMD 924A can be identical to ONU/T PMD 924B inembodiments using dual fibers between the OLT and an ONU/T.

The OSI application layer 903 in this embodiment is similar to FIG. 4A,however OLT Administration 904 does not use OMCI messages andcommunicates to Logical Link Control (LLC) entity 906 through OSInetwork layer entity known as user network interface-network side(UNI-N) 990A using network protocols such as Multiprotocol LabelSwitching (MPLS), for example, which can handle a plurality of networkadministration protocols between OLT Administration 904 and LLC 906. TheOLT data communications entity 450 and OLT NCSE 440 can also communicatewith LLC entity 906 using MPLS. The OLT NCSE 440 in some alternativeembodiments can communicate with LLC 906 using SNMP (e.g., when theyreside in an EMS, NMS or edge router).

In the OSI Data Link Layer or Ethernet MAC 901, packet switched networklayer communications, comprising of information exchanged between theOSI application layer and the data link layer, are mapped to frames ofIEEE 802.3 data link layer communications by the LLC entity 906. The LLCentity 906 multiplexes protocols transmitted to the OSI data link layerand decoding them while providing flow control and error control for thepacket-to-frame protocol conversion between the packets based OSInetwork layer and IEEE 802.3 frame based OSI data link layer. LLC entity906 processes communications between OLT Data Communications 450(comprising Ethernet OLT data) and OLT MAC client 908A, and LLC entity906 processes communications between OLT NCSE 442 (e.g., test methodmeasurement data) and OLT MAC client 908A. Additionally LLC entity 906processes communications between OLT Administration entity 904 and OLTMSE 916A comprising of Ethernet OAM frames, SNMP frames for FCAPSmanagement, OLT MIB and ONU/T MIB. OAM sub-layer entity 912 multiplexesand parses frames from MAC Client entity 908A and OAM Client entity 910Aand parses frames from MAC control sub-layer 914. OAM Client controlframes consist of OLT Administration entity 904 OAM messages whichinclude OLT MSE 916A OAM messages for embedding test parameters,allocating test measurement windows and extracting test measurements ortest results in synchrony with OAM Client traffic. Additionally, OAMSub-layer 912 exchanges frames with the MAC Control Sub-layer 914comprising of ONU/T data and test method communications, and comprisingof other OAM sub-layer specific frames used by the OAM sub-layer entity912 for processing link performance monitoring, alarm and statusmonitoring, loopback, OAM receive and transmission rule setting, ordiscovery of other OAM processing capable network terminalscapabilities. Once received frames are parsed they are either processedby the OAM sub-layer 912 or passed to the appropriate entity. Thesemultiplexing, parsing and control functions of the OAM sub-layer 912 canbe used by the OLT MSE 916A to discover the capabilities and addressesof other network terminals capable of performing test methods inresponse to OLT Administration entity 904 which is in communicationswith its peer OLT NCSE 440 through SNI 428. OAM frame processing canalso provide an OLT with an in synchrony mechanism for OLT NCSE 440 todiscover the capabilities and addresses of network terminals capable ofperforming test methods using services of the OLT Administration entity904. Once OLT MSE 916A is discovered and known to OLT NCSE 440, a testmethod can be performed by the OLT. To perform a test method involvinginsertion loss test, the OLT Administration entity 904 (responsive toOLT NCSE 440) can request the OLT MSE 916A to discover peer ONU/T MSE916B through the use of OAM sub-layer 912 processing communicated viathe OAM client entity 910A. Once peer ONU/T MSE 916B shares itscapabilities with OLT MSE 916A, the OLT MSE 916A responds to OLTAdministration entity 904 resulting in a servicing of the request fromOLT NCSE 440 for discovering ONU/T terminal capable of performing testmethods. Now that two MSE 251,254 (that share the same ODN) are known toOLT NCSE 440, test methods involving insertion loss can be performed bythe OLT. Also now that two MSE 251,254 (that share the same ODN) areknown to OLT NCSE 440, test methods can be initiated and performed bythe ONU/T. Furthermore, now both OLT and ONU/T network terminals can bemanaged by OLT NCSE 440 for test methods via OLT Administration entity904 services through SNI 428.

The MAC control sub-layer entity 914 is responsible for multiplexing,parsing and performing control functions for Ethernet PAUSE, Gate,Report, and Register REQ or ACK control frame processing for real-timecontrol and manipulation of IEEE 802.3 data link layer. MAC ControlSub-layer entity 914 can also support new functions such asencapsulating test method frames for performing and multiplexing testmethods along with test communication frames for reporting test methodmeasurements or results. Test method frame encapsulation and otherEthernet frame related information is discussed further in FIG. 10. Uponreceiving frames from OAM Sub-layer entity 912 (e.g., OAM frames, datacommunications or test method communications), receiving frames from theMAC control client 913 (e.g., MAC control frame parameters), andreceiving frame from MAC entity 918 (e.g., OAM frames, datacommunications, test method communications, MAC control frames), the MACControl sub-layer entity 914 parses the incoming frames to determinewhether it is destined for a specific function within the MAC Controlsub-layer entity 914 itself (e.g., MAC Control frame) such as processingPAUSE frames, Gate frames, Report frames, Register REQ or ACK frames andtest method frames or whether it is destined for one of theforementioned entities. The MAC entity 918 processes communicationsbetween MAC Control sub-layer entity 914 and the Reconciliationsub-layer (RS) entity 920 discarding malformed frames.

The 802.3 Physical Layer 900 is comprised of RS entity 920 that isresponsible for signal mapping between the MAC and PHY signal servicedomains (e.g. accommodations or adaptations of serial or parallel 1Gigabit (GMII) or 10 Gigabit Media Independent Interfaces (XGMII)). Thisreconciliation layer ensures that the Ethernet frames shown in FIG. 10are adapted for PCS/WIS processing. The reconciliation sub-layer entity920 interfaces with the PCS/WIS entity 922 which is responsible for theframe synchronization polynomial processing and other physical linecoding symbol processing and error event handing. The PMA entity 923provides a medium-independent means for the PCS/WIS 922 to support theuse of a range of physical media. The PMA entity 923 performs thefollowing functions: mapping of transmit and receive data streamsbetween the PCS or WIS and PMA via the PMA service interface;serialization (and de-serialization) of bits for transmission(reception) on the underlying serial PMD; recovery of clock from thereceived data stream; mapping of transmit and receive bits between thePMA and PMD via the PMD service interface; and optionally provides dataloopback at the PMA service interface.

The test method process will now be described for this embodiment fordownstream test methods (upstream test method process is similar withOLT MSE and OLT PLSE substituted for ONU/T MSE and ONU/T PLSE,respectively), the OLT NCSE 440 initiates a test method session andprovides test method parameters to OLT MSE 916A (e.g., using OAMmessage, SNMP FCAPS message). The OLT MSE 916A acknowledges the testmethod request and begins the process of performing the requested testmethod. The OLT MSE 916A can send a request (e.g., an Ethernet OAMmessage) to peer ONU/T MSE 916B requesting that it send a MAC ControlPAUSE frame which is processed by the MAC control sub-layer entity 914.A PAUSE frame is an IEEE 802.3x flow control mechanism which includesthe period of pause time being requested, in the form of a two byteunsigned integer which represents the duration of the pause. The unitsof measure for each bit of the pause time are called “quanta”, whereeach quanta unit is equal to 512 bit times. ONU/T MSE 916B can respondto peer OLT MSE 916A request for PAUSE frame generation by issuing a MACcontrol PAUSE frame through its ONU/T MAC control client entity 913.Once the OLT MAC Control Sub-layer entity 914 has received the MACcontrol PAUSE frame requested by OLT MSE 916A, all received frames arebuffered within the MAC Control Sub-Layer entity 914 until the PAUSEtime period (e.g. 802.3 PAUSE opcode pause_time request_operand) thataccommodates the test method has expired. This use of MAC control PAUSEframes enables the OLT MSE 916A to schedule test methods in synchronywith the IEEE 802.3 Data Link layer while maintaining continuity of datacommunications.

Once the MAC Control Sub-layer entity 914 has entered a PAUSE activestate and a test method is pending, the MAC Control Sub-layer entity 914can inform peer entity OLT MSE 916A that PAUSE state is active and canbegin to transmit test method frames with test method parameters(provided by the OLT MSE 916A). The test method frame passes through MACentity 918 and RS entity 920 to PCS/WIS entity 922. The PCS/WIS entity922 performs 8b/10b conversion of the test method frame to control codegroups. The PCS/WIS entity 922 responsive to test method parametersgenerates unique test method control code groups (e.g., “/L/” or“/K28.6/”) for the length of the test method covering the time reservedfor IS-Burst 626, DT 627, Test Method Sampling Window 628 and Restoreclock 629. The PMA entity 923 responsive to receiving the unique testmethod control group codes notifies the OLT PLSE 943A of the start ofthe IS-Burst 626 through PLSE interface. Additionally, it will beappreciated that during a test method the PCS/WIS entity 922 can ignoreor mask false PCS/WIS error events (e.g. LOS).

In alternative embodiments of the invention, the PCS/WIS entity 922encode and decode states can include multiple test method code groupextensions to incorporate the test method events. For example, the testmethod IS-Burst period 626, DT 627, and test measurement window period628 can each be delineated by their own unique test method control codegroup by the PCS/WIS entity 922 and the PMA 923 can pass the timing ofthese delineation by control code group extensions to the PLSE throughthe PLSE interface. In yet another alternative embodiment, it will beappreciated that the PMA entity can transmit one or more test methodcontrol code groups to notify the receiving peer PMA entity of theimpending start of the IS-Burst period and subsequent transition of thetest signal. The receiving peer PMA entity can use this notification toignore or mask false LOS signal.

Referring now to FIG. 10 in view of FIG. 9A and FIG. 9B, an exemplaryblock diagram illustrating a diagrammatic flow of the communications ofan embodiment of the invention for IEEE 802.3 P2P Ethernet optical fibernetworks such as those based on IEEE 802.3z GE or IEEE 802.3ae 10GE isshown. For IEEE 802.3 P2P Ethernet frames, the downstream and upstreamframe formats are the same, FIG. 10 represents both downstream andupstream frames. Ethernet frame 1000 represents standard Ethernet dataframe. Ethernet frame 1004 further details and represents an EthernetOAM frame and Ethernet frame 1008 further details and represents anEthernet MAC Control frame. Ethernet frame 1002 is an embodiment of anEthernet frame representation of a test method frame. In thisembodiment, the Ethernet frame type for MAC Control frame 1044 is usedwith a unique MAC Control Test Opcode 1055 that distinguishes testframes from other MAC control frames. In alternate embodiments, a uniqueEthernet frame type can be used instead of MAC Control frame type 88-081044 with similar frame field elements as shown in test method frame1002.

In the embodiment of test method frame 1002 shown in FIG. 10, the testmethod frame 1002 field elements are generated and processed by datalink layer and physical link layer as previous discussed in FIG. 9A andFIG. 9B for IEEE 802.3 P2P Ethernet networks. The MAC Control TestMethod OpCode 1055 can be used to uniquely identify the type of testmethod being performed and test method parameters can be included withinthe MAC Control Test Method Parameters field 1056. As previouslydiscussed test method parameters can included, but not limited to, testmethod type, length of test burst window period, length of delay period,measurement sampling rate, bit clock recovery pattern or sequence to beused, and duration of the restore clock. Additionally test methodparameters can include information or bit indicators to select testmethod options such as optical intensity (i.e., optical power),frequency or pattern of one or more transmissions of light and theirdurations as well as the sampling resolution of test light transmissionmeasurements for the test method. Pad field 1057 follows MAC ControlTest Method Parameter 1056 field and is used to insert or pad bits inthe test method frame to align to an Ethernet nibble structure inpreparation for Frame Check Sequence (FCS) field 1058. FCS is a checksumfor MAC control frames and is the last four octets of the MAC controlframe portion of the test method frame 1002. IS Burst 626, DT 627, TestMethod Sampling Window 628 and Restore Clock 629 follows to completetest method frame 1002 in this embodiment. Again, Restore Clock 629 isan optional field and need not occur in all embodiments of theinvention. In alternative embodiments, the test method frame can endwith Test Method Sampling Window 628 and the idle control group symbolsof the interframe gap (IFD) 1010 can be used for clock or bit levelsynchronization

Following test method frame 1002 an End of Packet Delimiter (EPD), asdefined in IEEE 802.3 clause 24.2.2.1, is transmitted by PCS/WIS entity922 following the de-assertion of transmit enable which corresponds tothe last data nibble composing the FCS field 1058 from the MAC entity918. EPD is transmitted during the period considered by Ethernet MAC tobe the interframe gap (IFG) 1010. On reception of non-test methodframes, EPD is interpreted by the PCS/WIS 922 as terminating IEEE 802.3service data unit (SDU). It will be appreciated that in order topreserve the ability of IEEE 802.3 MAC to properly delimit the FCS atthe end of the frame (that is, to avoid incorrect alignment errors inthe MAC) the internal MAC entity 918 signal receiving (and through RSentity 920 per Clause 22) is de-asserted immediately following the lastcode-bit in the stream that maps to the FCS 1058 (e.g., “/T/R” codes).Note that the condition IEEE 802.3 “link status” variable is “NOT OK”during stream reception (that is, when “receiving” variable is “TRUE”)causes an immediate transition to the LINK FAILED state and supersedesany other Receive process operations. However this transition into LINKFAILED state is delayed for test method frames 1002 to accommodate theremaining bit times or symbol periods required to complete the remainingtest method fields such as IS Burst 626, DT 627, ISOTDR and ISOTDR-ISILSampling Window 628 and restore clock 629 described previously. Forexample, on reception of a test method frame FCS field 1058, EPD istransmitted after the last bit time or symbol period of the restoreclock field 629 or in alternative embodiments after the test methodsampling window has passed. It will be appreciated that by delayingtransmission of EPD the PMD clock recovery phase-lock-loop circuitry isallowed to recover phase and bit lock, thus preserving the ability ofIEEE 802.3 MAC to properly delimit the test frame 1002 restore clockfield 629 or in alternative embodiments interframe gaps. In someembodiments of the invention, alternate schemes for transitioning intoEPD can be performed based on masking LOL and LOS signal states of theCDR as previously discussed in FIG. 6A. Regardless of what transitionscheme used for test method frames 1002 to transmit EPD, the receivingterminal can retain IEEE 802.3 interframe gap (IFG) 1010 processing. Insummary, FIG. 10 test method frame 1002 fields shown represent anexemplary embodiment that is in synchrony with IEEE 802.3 P2P Ethernetprotocol framing.

Referring now to FIG. 11A which illustrates a table containing a subsetof the PCS control group codes used in IEEE 802.3 Ethernet. Aspreviously mentioned a unique PCS control group code can be used toinform the PMA layer of the test method being performed. For example,the control code “/L/” using the control group coding “/K28.6/” can beused to identify to the PMA layer 923 when to perform a test method. ThePMA layer 923 upon receiving the “/L/” code then knows when to begin thetest method. Prior to receiving the “/L” code the PMA is configuredthrough station management 925 to perform the test method. Test methodconfiguration includes, as previously discussed, test method parameterssuch as the length of the test signal burst, length of the delay timeperiod, and other test method parameters (e.g., test signal frequency orpattern, sampling rate and resolution).

Referring now to FIG. 11B in view of FIG. 9A-11A, an illustration of thecommunication flow between PCS, PMA and PMD layers in relation toperforming a test method is summarized. Starting with a test methodframe 1002 received by the PCS 922 in an active PAUSE time period, thePCS 922 performs 8b/10b encoding on the test method frame 1002 and thengenerates unique test method control code groups (e.g. “/L” codes) forthe length of the test method responsive to the type 88-08 field 1044,MAC control test method opcode 1055 and MAC control test methodparameters 1056 which informs the PCS 922 of the length of the testmethod. The PMA 923 serializes the 8b/10b encoding and responsive toreceiving unique test method control code groups (e.g., “/L” codes) andsignals though PLSE interface entities in the PMD layer (e.g., PLSE) toperform the test method. The PMD entities (e.g. PLSE) can bepreconfigured to perform the test method through station managementprogrammed via PMD control 927.

Referring now to FIG. 11C, which illustrates the block level circuitryand physical and data link layers of an OLT 1100 and an ONU/T 1101embodiment of an IEEE 802.3 P2P active Ethernet network in view of FIGS.3, 5, 8, and 9A-11D. Ethernet MACs functioning as an OLT and ONU/Tcomprise an OLT MSE and ONU/T MSE, respectively, as previouslydiscussed. The OLT MSE and ONU/T MSE communicate through stationmanagement to PCS and PMA layers, respectively. The PMA communicates tothe OLT PLSE and ONU/T PLSE through a PLSE interface. The OLT PLSE andONU/T PLSE, responsive to the timing provided by the PMA in someembodiments or responsive to test method configuration through stationmanagement in other embodiments, can mask LOS and LOL signals, controltransmitter output including disabling or turning off the transmitter,pre-charging an APD, storing IL sample measurements (e.g., RSSI values),and storing OTDR and OFDR sample measurements as well as sending samplemeasurements back to the Ethernet MACs through PMA via the PMD controlbus or via the PLSE interface. It will be appreciated that OLT PLSE andONU/T PLSE can be embodied by state machine circuitry and logic as partof a System-on-a-Chip (SOC) or a microcontroller and software. It willalso be appreciated that embodiments of OLT PLSE and ONU/T PLSE cancomprise registers to store test method configuration (e.g., asconfigure through station management) as well as counters used toprovide timing or bit counting of test method sections (e.g., IS Burst626, DT 627, sampling window 628 and restore clock 629) to perform testmethods.

Referring now to FIG. 11D, an exemplary embodiment of a method forincorporating in-service diagnostic or test methods in thecommunications of IEEE 802.3 P2P active Ethernet networks in view ofprevious discussions and in view of FIGS. 9A-11C is summarized. Startingwith requesting a test method 1180, by a peer application entity (e.g.,EMS, NMS), to be performed between an OLT and the ONU/T the OLT NCSE(e.g., OLT NCSE 440) initiates a test method responsive to the request.The OLT NCSE then processes the request to establish test methodparameters (e.g., ONU/T address, test type, test signal frequency orpattern, sampling rate, and other parameters as previously discussed)and initiates the test method by sending, for example, an OAM message1182 to OLT MSE (e.g., OLT MSE 916A) or ONU/T MSE (e.g., ONU/T MSE916B). The OLT MSE configures the OLT PMD or the ONU/T MSE configuresthe ONU/T PMD to perform the test method (e.g., type of test method,length of test signal burst, length of delay time period, test signalfrequency or pattern, clock recovery pattern) by configuring the OLT PMD924A or ONU/T PMD 924B though station management 917 (e.g., throughMDIO, I²C or equivalent). The OLT MSE 916A or ONU/T MSE 916B requeststheir peer MSE to issue a MAC control PAUSE frame using OAM messages.The peer MSE then, responsive to the request, schedules a test method bysending a PAUSE frame request message to its peer MAC control sub-layerentity 914 though its peer MAC client control entity 913. The peer MACcontrol sub-layer entity 914 then generates and sends in synchrony withEthernet communications MAC control PAUSE frame 1184 which establishes aPAUSE time period on reception of the MAC control PAUSE frame by OLTMSE's 916A or OLT MSE's 916B MAC control sub-layer entity 914. The testmethod frame 1002 is then generated in synchrony with Ethernetcommunications by the MAC control sub-layer entity 914 with contributionfrom the OLT MSE 916A or ONU/T MSE 916B and sent through the RS layer920 to the PCS layer 922. The PCS 922 responsive to receiving the type88-08 field 1044, MAC control test method opcode 1055 and MAC controltest method parameters 1056 generates test method control group codes(e.g., “/L”) which inform the PMA 923 when to begin the IS Burst 626portion of the test method 1186. After the test method event, the PAUSEperiod ends and communications continue having maintained synchrony andcontinuity of communication flows through the test method event. Testmethod results are sent 1188 through Ethernet payloads to the OLT NCSEas previously discussed.

It will be appreciated that embodiments of the invention using IEEE802.3ah EPON are similar to FIG. 9A-11D with the exception of utilizingMultipoint MAC Control Protocol (MPCP) control frames instead of MACcontrol frames. MPCP control frames 1308 are used to issue MPCP controlPAUSE frames (i.e., establish PAUSE time periods) which are scheduled byan MSE to perform test methods. It will also be appreciated that while asingle control group code “/L” was described along with test methodconfiguration management through station management, alternativeembodiments can utilize additional control group codes between the PCSand PMA layers to delineate segments of the test method frame (e.g., ISBurst 626, DT 627, Sampling Window 628, Restore clock 629).

Referring now to FIG. 12A and FIG. 12B, in view of FIG. 9A and FIG. 9B,exemplary embodiments of the invention of an OSI reference models andrelated entities for an OLT 1400 and ONU/T 1401, respectively, for IEEE802.3av 10G-EPON networks is shown. FIG. 12A and FIG. 12B entities willbe discussed in relation to FIG. 9A and FIG. 9B. LLC entity 1206performs similar functions to LLC entity 906 with the additionalfunctionality of multiplexing communications and assigning LLIDs (usedto address specific ONU/Ts) between multiple MAC Clients 1208 a-n. TheOLT Ethernet MAC 1201 has multiple MAC client entities 1208 a-n whereineach MAC client performs similarly to MAC client entity 908 a. OAMsub-layer entity 1212 performs similar functions to OAM sub-layer entity912 with the additional functionally of handling multiplexing andaddressing for multiple MAC clients. MPCP sub-layer entity 1214 performssimilar to MAC control sub-layer entity 914 with the additionalfunctionality of messages, state diagrams and timers to control accessto the point-to-multipoint (P2MP) topology of the PON network among theN number of MACs 1218 a-n. RS layer entity 1220 has the additionalfunctionality of multiplexing communications to and from multiple MACs1218 a-n to the PCS layer entity 1222. PCS layer entity 1222 hasadditional functionality, for example, of communicating when to turningon and off the transmitter for IS Burst 626, when to begin measurements,and receiving test method measurements in one embodiment of the presentinvention. In alternative embodiments, a PLSE can be configured toperform a test method through station management 917 using PMD control927 and receives notification from the PCS layer entity 1222 of when tobegin performing the test method, similarly as previously discussed.

Referring now to FIG. 13A and FIG. 13B in view of FIG. 10, downstreamand upstream test method frames use MPCP control test method frames 1302to indicate the test method type (e.g., MPCP control test method opcode1355) and convey test method parameters (e.g., MPCP control test methodparameters 1356).

Referring now to FIG. 14A and FIG. 14B in view of FIG. 11B, the PCSlayer 1222 responsive to MPCP control test method frames 1302 has theability to communicate with the PMD layer and PLSE through the PLSEinterface to perform the test methods similarly as previously discussed.

Referring now to FIG. 14C in view of FIG. 11C, FIG. 14C is a blockdiagram which illustrates the block level circuitry and physical anddata link layers of an OLT and ONU/T of a point-to-multipoint IEEE10GE-PON Ethernet optical fiber data network in accordance with anembodiment of the present invention. FIG. 14C illustrates 10G-EPON MACand PHY layers and associated entities for OLT 1400 and ONU/T 1401 aswell as illustrates a PON fiber plant 501-503.

Referring now to FIG. 14D, it will be appreciated that downstream testmethods in 10G-EPON perform similarly to test methods performed in P2PEthernet. As mentioned previously, PAUSE time periods are still used toschedule test methods however PAUSE time periods are established withMPCP control frames 1308. Test methods in the upstream direction differwith the addition of the use of MPCP control GRANT frame for allupstream communications. Starting with requesting a test method 1480, bya peer application entity (e.g., EMS, NMS), to be performed between anONU/T and the OLT the OLT NCSE (e.g., OLT NCSE 440) initiates anupstream test method responsive to the request. The OLT NCSE processesthe request to establish test method parameters (e.g., ONU/T address,test type, test signal frequency or pattern, sampling rate) andinitiates the test method by sending, for example, an OAM message1004,1304 to ONU/T MSE (e.g., ONU/T MSE 1216B). The ONU/T MSE uses testmethod parameters from the OAM message to configure the ONU/T PMD toperform the test method (e.g., type of test method, length of testsignal burst, length of delay time period, test signal frequency orpattern) by configuring the ONU/T PMD 1224B though station management(e.g., though MDIO, I²C, or equivalent). The ONU/T MSE 916B sends (afterreceiving an upstream GRANT 1482) an OAM message to schedule or requesta PAUSE time period to the OLT MSE 916A which then requests the OLT MPCPcontrol sub-layer entity 1214 through OLT MAC client control entity 1213to generate and send in the downstream an MPCP control PAUSE frame backto the ONU/T 1484. The test method frame 1302 is then generated by theONU/T MPCP control sub-layer entity 1214 (with contribution from ONU/TMSE as previously discussed) and sent (after receiving an upstreamGRANT) in synchrony with Ethernet communications through the RS layer1220 to the PCS layer 1222. The ONU/T PCS 1222 responsive to receivingthe type 88-08 field 1344, MPCP control test method opcode 1355 and MPCPcontrol test method parameters 1356 communicates with the ONU/T PLSEthrough PLSE interface to perform the test method 1486. After the testmethod event, the PAUSE period ends and communications continue havingmaintained synchrony and continuity of communication flows through thetest method event. Test method results are encapsulated and sent 1488through Ethernet payload to the OLT NCSE as previously discussed. Itwill be appreciated that upstream communication GRANT allocations areneeded in the upstream to perform upstream test methods as well assending the OAM request for a PAUSE frame and as well as for sendingtest method results. It will also be appreciated that in an alternativeembodiment the OLT NCSE 440 can send an OAM message to the OLT MPCPcontrol sub layer entity 1214 to request a PAUSE time period eliminatingthe need for an ONU/T MSE 1216B to send an OAM message to the OLT MSE1216A which then sends a request for a PAUSE time period to the OLT MPCPcontrol sub layer entity 1214.

It will be appreciated that in some P2P Ethernet embodiments,embodiments of the PCS/WIS entity can generate PMD transmission statevariables which are passed to a PLSE entity (e.g., via a PLSEinterface). The PMD transmission state variables can be Boolean (i.e.,true or false) variables that allow the PCS portion of the PCS/WISentity to notify the PMA entity below of the start of a test methodframe as well as to notify the PMA about delineate transitions of thesub-sections of the test method frame. For example, PMD transmissionstate variables can be generate for one or more of the followingtransitions: test method frame transition from FCS 1058 to IS-Burst 626or the first transmitted unique test method control code group (e.g.,“/L”); the transition from the end of IS-Burst period 626 to the startof DT period 627; the transition from the end of Delay Time period 627to the start of Test Method Sampling Window 628; the transition from theend of the Test Method Sampling Window 628 to the start of the optionalRestore Clock period 629; and the transition from the end of theoptional Restore Clock period 629 to the start of Interframe Gaptransmission 1010 (e.g. PCS transition from unique test method controlgroup “/L/” to the start of end of packet control group “/T/”, carrierextend control group “/R/”, and idle control group “/I/” transmission).These PMD transition state variables are processed by the PMA in amanner that accounts for the processing time of the WIS portion of thePCS/WIS entity. An MSE entity, responsive to receiving test methodparameters from an NCSE entity, can configure how these PMD transmissionstate variables are used by configuring PCS/WIS, PMA, PMD and PLSEentities via station management.

It will be appreciated that while various P2P Ethernet embodiments(e.g., active Ethernet) and P2MP Ethernet embodiments (e.g., EPON andXG-EPON) have been discussed using the PAUSE flow control mechanism ofIEEE 802.3x (e.g., MAC control PAUSE frames for active Ethernetembodiments, MPCP control PAUSE frames for EPON and XG-EPONembodiments), alternative embodiments of the invention can use MACcontrol Priority PAUSE frames or MPCP control PAUSE frames as well,respective of the embodiment. Priority-based flow control, as defined bythe standard IEEE 802.1Qbb (included herein by reference) provides alink level flow control mechanism that can be controlled independentlyfor each Class of Service (CoS), as defined by IEEE 802.1p (includedherein by reference).

It will also be appreciated that PAUSE flow control mechanism of IEEE802.3x and Priority PAUSE flow control mechanisms of IEEE 802.1Qbb canbe used in GPON and XG-PON embodiments (e.g., FIGS. 4A-7C and relateddiscussions) as well. Referring now to FIG. 4A and FIG. 4B, Ethernet LLC& MAC entity 422 can issue MAC control PAUSE frames (or MAC controlPriority Pause frames) to generate PAUSE time periods between EthernetLLC & MAC entity 422 (e.g., in OLT GTC Adaptation Layer 402A) and peerEthernet LLC & MAC entity 422 (e.g., in ONU/T Adaptation Layer 402B) andvice versa. The PAUSE flow control mechanisms or Priority Pause flowcontrol mechanisms in these embodiments are effective at or across theUNI interfaces 421,461. The MAC control PAUSE frame (or MAC controlPriority PAUSE frame) can be issued at the request of an MSE. The MSE(e.g., OLT MSE 416A, ONU MSE 416B) issues the request by sending an OAMmessage to Ethernet LLC & MAC entity 422 through Embedded OAM entity 418and OAM channel adaptation entity 427 responsive to receiving a testmethod request from an NCSE (e.g., OLT NCSE 440, ONU/T NCSE 480). Oncethe PAUSE time period has been established between network terminals,test methods can be performed in the PAUSE time period similarly aspreviously discussed in references to FIG. 4A-7C for GPON and XG-PONembodiments of the invention.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. They are not intended to be exhaustive or to limitthe invention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. Accordingly, it is to beunderstood that the drawings and descriptions herein are proffered byway of example to facilitate comprehension of the invention and shouldnot be construed to limit the scope thereof.

1. A network terminal for an optical fiber network disposed to havingone or more optical fibers to couple to network terminal, the networkterminal having an optical transceiver for coupling to the opticalfibers, and the optical transceiver having a first optical receiver forreceiving optical data signals on a first wavelength and the opticaltransceiver having an optical transmitter for transmitting optical datasignals on a second wavelength and the optical transceiver having asecond optical receiver for receiving optical signals on the secondwavelength and the network terminal having a controller coupled to theoptical transceiver and for communicating using a network protocolhaving predetermined time intervals or frames for data communicationswith other network terminals, a method of performing opticalmeasurements of the optical fiber using the second wavelength comprisingthe steps of: (a) scheduling by the controller a test interval ofpredetermined time in synchrony with the predetermined time intervals orframes of the network protocol, the test interval comprising a firsttime interval for transmitting an optical test signal followed by asecond time interval for turning off the optical transmitter followed bya third time interval for measuring the optical test signal; (b) duringthe first time interval of the test interval, transmitting the opticaltest signal on the second wavelength by the optical transmitter onto anoptical fiber; (c) during the second time interval of the test interval,turning off the optical transmitter resulting in no further lighttransmissions on the optical fiber; (d) during the third time intervalof the test interval, measuring a portion of the optical test signal onthe second wavelength by the second optical receiver; and (e) turning onthe optical transmitter after the test interval and transmitting opticaldata signals for communicating to another network terminal, whereby theoptical network terminal is disposed to perform optical measurementswhile the network terminal is in-service and the continuity of datacommunications is maintained by scheduling, transmitting and measuringthe optical test signal in accordance and in synchrony withpredetermined time intervals or frames of the network protocol.
 2. Themethod of claim 1, wherein the test signal includes one or more lighttransmissions, each comprised of a desired pattern of intensity,frequency, and duration.
 3. The method of claim 1, wherein the opticalfiber network includes at least one of the following group: apoint-to-point optical fiber network; and a point-to-multipoint opticalfiber network.
 4. The method of claim 1, further comprising the step of:(f) analyzing the measured portion of the optical test signal todetermine at least one of the following group: conditions of one or moreoptical fiber links; transmitter optical coupling efficiencies of thenetwork terminal; optical fiber link tampering; microbends in one ormore optical fiber links; macrobends in one or more optical fiber links;optical return loss of the network terminal; mean launch power of thenetwork terminal; location and characteristics of impairments such asoptical fiber splices, optical fiber connectors, optical splitters, andoptical fiber segment loss in one or more optical fiber links; insertionloss between the first network terminal and a second network terminaloptically coupled to the first network terminal; and reflectance of thesecond network terminal optically coupled to the first network terminal.5. The method of claim 1, further comprising at least one step from thefollowing group: performing an optical time domain reflectometryanalysis responsive measuring a portion of the transmitted optical testsignal on the second wavelength by the network terminal; performing anoptical frequency domain reflectometry analysis responsive measuring aportion of the transmitted optical test signal on the second wavelengthby the network terminal; performing an insertion loss analysisresponsive to measuring a portion of a transmitted optical test signalon the first wavelength by the network terminal; and analyzing themeasured portion of the transmitted optical test signal to determineoptical return loss at the network terminal.
 6. The method of claim 1,further comprising the step of: performing the optical test signaltransmitting step responsive to one or more of the following conditions:responsive to communications from the network terminal beingunderutilized; in lieu of idle packets or silence periods; andresponsive to a disruption in communications of the network terminal. 7.The method of claim 1, wherein the optical test signal includesinformation on the duration of the test interval.
 8. The method of claim1, wherein the second optical receiver of the network terminal includesan avalanche photo-diode (APD).
 9. The method of claim 1, whereinnetwork protocol flow control mechanism available at the networkterminal are used to schedule the test interval.
 10. The method of claim1, wherein a unique identifier used to identify traffic is associatedwith the test interval.
 11. A method for performing analyticalmeasurements of optical fiber links of an optical fiber network, theoptical fiber network disposed to having one or more optical fiber linksto couple data signals between two or more network terminals, and thenetwork terminals having network protocols for communicating the datasignals, and the network protocols having predetermined time intervalsor frames and flow control mechanisms for communication on one or morecommunication signal wavelengths over the optical fiber network, themethod comprising the steps of: in synchrony with the flow controlmechanism and predetermined time intervals of the network protocol,transmitting on a communication signal wavelength over a first opticalfiber link from a first network terminal to a second network terminal anoptical test signal followed by a predetermined time interval whereinthe optical transmitter of the first network terminal is disabled;detecting and measuring a portion of the transmitted optical test signalreceived at the first or second network terminal during thepredetermined time interval wherein the optical transmitter of the firstnetwork terminal is disabled to analytically measure the operation ofthe first optical fiber link between the first network terminal and thesecond network terminal; enabling the optical transmitter at the firstnetwork terminal after the predetermined time interval and continuingcommunications from the first network terminal on the communicationsignal wavelength over the first optical fiber link wherein the flowcontrol mechanisms of the network protocol have maintained continuity ofthe communications, whereby the optical fiber network disposed to havingone or more network terminals is disposed to analytically measure one ormore optical fiber links of the optical fiber network while the opticalfiber network is in-service and maintaining data communications betweennetwork terminals by transmitting and measuring a test signal insynchrony with the flow control mechanisms and predetermined timeintervals or frames of the network protocol.
 12. The method of claim 11,wherein the optical test signal includes one or more lighttransmissions, each comprised of a desired pattern of intensity,frequency, wavelength and duration.
 13. The method of claim 11, whereinthe optical fiber network includes at least one of the following group:a point-to-point optical fiber network; and a point-to-multipointoptical fiber network.
 14. The method of claim 11, further comprisingthe step of: analyzing the measured portion of the transmitted opticaltest signal to determine at least one of the following group: conditionsof one or more optical fiber links; transmitter optical couplingefficiencies of the first network terminal; optical fiber linktampering; microbends in one or more optical fiber links; macrobends inone or more optical fiber links; insertion loss between the first andsecond network terminals; optical return loss of the first networkterminal; reflectance of the second network terminal on the firstoptical fiber link; reflectance of a third network terminal on a secondoptical fiber link between the first terminal and the third networkterminal; mean launch power of the first network terminal location andcharacteristics of impairments such as optical fiber splices, opticalfiber connectors, optical splitters, and optical fiber segment loss inone or more optical fiber links.
 15. The method of claim 11, furthercomprising at least one step from the following group: performing anoptical time domain reflectometry analysis responsive to measuring aportion of the transmitted optical test signal at the first networkterminal; performing an optical frequency domain reflectometry analysisresponsive to measuring a portion of the transmitted the optical testsignal at the first network terminal; performing an insertion lossanalysis responsive to measuring a portion of the transmitted theoptical test signal at the second network terminal; and analyzing ameasured portion of the transmitted optical test signal to determineoptical return loss at the first network terminal.
 16. The method ofclaim 11, further comprising the step of: performing the optical testsignal transmitting step responsive to one or more of the followingconditions: when communications between network terminals are beingunderutilized; in lieu of idle packets or silence periods; andresponsive to a disruption in communications between the networkterminals.
 17. The method of claim 11, wherein the optical test signalincludes information on the duration of the optical test signal and thepredetermined time interval wherein the optical transmitter of the firstnetwork terminal is disabled.
 18. The method of claim 11, wherein one ormore network terminals of the optical fiber network are disposed toinclude avalanche photo-diode (APD) to measure a portion of thetransmitted optical test signal.
 19. The method of claim 11, whereinPAUSE frames of the network protocol flow control mechanism are used togenerate PAUSE time periods during which the optical test signal istransmitted, the optical transmitter is disabled, and measurements ofthe optical test signal are performed.
 20. The method of claim 11,wherein the optical test signal is used to generate unique Ethernetcontrol code groups by the PCS layer to indicate to the PMA layeraspects of the optical test signal and test interval.